Updated: Aug 14, 2019
Not too long ago WiFi was an afterthought for companies. Now, desktop sales are on the decline and most people are only plugged in when they have to be. Add to that, mobile phones, tablets, and guest devices, and you can quickly have hundreds of devices for which to provide access.
The default corporate setup usually a "secured" WiFi with Radius authentication and a "Guest" WiFi with an Internet only connection. This works fine until you are dealing with bigger numbers of devices. Before performance begins to suffer, I would suggest making a few changes.
Most importantly, use VLANs to segment your wired LANs from your Wireless networks. Keep your phones and tablets in their own separate wireless network from Laptops. Use MDM to assign a different SSID to your mobile devices and segment to a separate VLAN. If your company relies on bar code scanners or handhelds or POS or wireless printers, keep those on their own SSID, too. This will only help clean things up for this group of devices. If you need higher performance for certain applications (voice/video) or devices ("Cordless" VOIP Phones), consider dedicating specific hardware (access points and radios) to a "VIP" WiFi. Quality of Service (QoS) is great once traffic hits the wire, but all WiFi is considered equal from the perspective of the antennas, radios, and the access points. If your environment has enough coverage, or if you have budget to add, setup some radios to only broadcast your VIP WiFi and you will help throughput for those important devices and apps.
5G and WiFi6 are coming in the next several years and these technologies will certainly change the game. Ushering in a true "mobile first" infrastructure, 5G and WiFi6 will add magnitudes of speed and performance for Mobile Devices and Wireless clients. With 5G, my hope is that the need for Guest access will die out. Cellular coverage and performance should be high enough that joining a guest network will seem slower and pointless. With WiFi6 we should be seeing network performance improvements similar to the hub-to-switch upgrades back in the Y2K days. WiFi6 brings in a multiplexing technology that has not been possible until now. At first, WiFi6 will most likely be limited for Universities, Airports, Stadiums, Hospitals, Conference Centers and other venues where large amounts of devices are connected. It may take several more years for prices to come down to the point where a home would have WiFi6, but I will gladly upgrade when I can.