Technical Tip: WI-FI capacity calculation
Description
This article describes and explains how to calculate the real capacity of devices per radio based on association rates.
Scope
FortiAP, FortiGate.
Solution
Causes of performance issues:
Association rates are dynamic.
Good SNR means maximum possible association rate.
Due to management and control frames, typical WiFi net throughput is 30 to 40 percent from the association rate on most well-tuned networks.
WiFi throughput often cannot be the same as most wired networks.
Performance example and capacity calculation:
Most multimedia applications require a minimum of 4 Mb/s per user for an ideal collaboration experience.
For more network preparation details, consult every application requirement in the Microsoft recommendations:
Bandwidth requirements (for Zoom).
On a 20 MHz cell using SGI, up to 7 1x1:1 AC MIMO devices can use Teams efficiently.
This calculation is obtained by taking 72 Mb/s of the association rate, multiplying it by 40 percent WiFi spectrum efficiency, and dividing the result by the 4 Mb/s required, which gives a total of 7 devices.
By using only 3x3:3 MIMO WiFi devices on a 4*4 MIMO FortiAP, it is possible to increase the capacity up to 21 devices per radio.
When performing performance calculations, network architects must consider the capacity of the most critical device with the most limited specifications, using the network's most critical application (known in specialized literature as the most important, least capable device).