Technical Tip: Factors that can cause high channel utilization on the FortiAP

Channel Utilization is the primary indicator of Wireless Capacity on the FortiAP radio. The following factors can increase the channel utilization on the FortiAP, affecting the WiFi performance:

1. Co-channel interference on the FortiAP is due to improper channel planning on the FortiAPs and high transmit power from neighboring FortiAPs.
2. There is a high client load on the FortiAP radio due to poor FortiAP placements and High Transmit Power, which causes client load balancing and sticky client issues on the FortiAPs.
3. Poorly connected legacy WiFi clients on the FortiAP channel with low data rates cause longer airtime and eventually keep the channel busy.
4. WiFi client traffic type sent on the FortiAP channel, i.e., Bandwidth-intensive applications traffic (E.g., Audio-Video Streaming/iPerf/Torrentz/Multicast services/Video conferencing) over WiFi.
5. A large amount of data is being sent by a certain user(s) on the FortiAP channel.
6. Narrow channel width on the FortiAP radio. At least a 40 MHz or higher channel width can be used for a high-user-density setup.
7. Constant Radar pulses of RF energy on the 5 GHz band on the FortiAP.
8. 3rd party WiFi interface sources (E.g., WiFi hotspots/Microwave/Bluetooth/Cordless phones/Wireless cameras).
9. As a general best practice, use the FortiAP and FortiGate (optional) on the latest v7.4 or v7.6 GA release, as the newer FortiAP firmware versions contain multiple WiFi stability fixes 
10. For the FortiAP and FortiGate firmware compatibility matrix. Refer to FortiAP and FortiOS 7.x Compatibility Matrix

From 1 to 8, the best way to deal with the situation and most WiFi-related issues is to perform an RF site survey to determine the best configuration options and configure FortiGate and FortiAP as directed by the study results.

Technical Tip: RF Design for Wireless Networks

In the meantime, channel utilization can be improved by using the following recommendations and then fine-tuning related configs using study results when available:

1. Conduct RF Site Survey pre and post FortiAP WiFi installation to identify and minimize sources of interference in the environment.
   
   
2. Use DARRP efficiently: Troubleshooting Tip: DARRP channel assignment on FortiAP WiFi.
   
   
3. Use Auto Tx power and resolve bad FortiAP placement:

Enabling automatic TX power control

Technical Tip: FortiAP not auto adjusting the Tx power and always operating on the Maximum power set in the range

Technical Tip: Avoid bad practices when placing FortiAP

4. Customize data rates as directed by study results:

   Features for high-density deployments

    

    

5. Use Broadcast filters and Multicast enhancement on all SSIDs:

   Configuring the broadcast packet suppression

   Converting multicast streams to unicast

    

    

6. Download 'WiFi Events' logs from FortiGate to find Radar/DFS events and refer to the steps to minimize Radar hits on the FortiAP: Troubleshooting Tip: How to debug Radar detection issue on the FortiAP WiFi

    

7. The latest FortiAP v7.6.4 build 1078 GA firmware contains a fix for the following known issue: debug any ongoing High Channel Utilization issues on top of FortiAP v7.6.4 GA firmware.
   

    

   1116110: Some Wi-Fi clients with RealTek chipsets had high channel utilization when 802.11ax was enabled.
   FortiAP 7.6.4 GA Resolved issues

    

    

8. Ensure the laptops' WLAN chipset drivers are running on the latest versions; using older, outdated drivers on the WiFi clients may consume unwanted airtime and keep the channel busy, increasing the channel utilization on the FortiAP.

    

Contact the laptop vendor support for the latest drivers:

Intel® Wireless Wi-Fi Drivers for Windows® 10 and Windows 11

Lenovo WLAN Driver (Intel, Realtek) for Windows 11

HP Software and Drivers

Dell Wireless drivers