Unstable Wi-Fi Speed Across FortiAPs Despite Good Wired Throughput

[Abu_Ryan]

Hello Fortinet Community,

We are facing a persistent issue with Wi-Fi performance in our office building and would appreciate some guidance or suggestions to resolve it.

Environment Setup:

• Building Floor: 3 adjacent offices on the same floor.

• FortiAP Deployment:

  • Office 1:  single 221E FortiAP

  • Office 2: Two 231G FortiAPs

  • Office 3: Single 431F and Two 221E FortiAPs

• Total FortiAPs: 6 (all managed via FortiGate)

• ISP Plan: 750 Mbps

• Firewall & Switches: FortiGate 400E and Cisco SGS 350 (getting full speed at wired data points)

Issue:

While we consistently receive full bandwidth (750 Mb) at wired endpoints, Wi-Fi-connected devices experience unstable and poor performance. The wireless speed varies significantly:

• Often drops to 30–50 Mb

• Occasionally goes up to 100–200 Mb

• Never reaches anywhere close to the wired speeds

• Behavior is the same even in none business hours, with no user load on the network

Troubleshooting Done:

• Upgraded firmware of all FortiAPs to the latest version

• Adjusted radio channel settings to avoid interference, enabled band steering.

• Checked with both Tunnel and Bridge mode by creating a test SSID.

• Checked for client load and signal strength per AP 

Despite these efforts, the issue still persists. We’re trying to identify if the root cause lies in interference, AP placement, configuration, or any controller-side issue.

Any insights, recommendations for diagnostics, or best practices would be greatly appreciated.

Thanks in advance!

Regards,

Aslam

[Jean-Philippe_P]

Hello Abu_Ryan, 

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible. 

Thanks, 

[Abu_Ryan]

Thank You Brother.

[Jean-Philippe_P]

Hello,

We are still looking for an answer to your question.

We will come back to you ASAP.

[Jean-Philippe_P]

Hello again Abu_Ryan,

I found this solution. Could you please let me know if it helps?

To address the Wi-Fi performance issues in your office building, consider the following steps:

1. Site Survey and AP Placement:
   - Conduct a thorough site survey to ensure optimal placement of your FortiAPs. This will help identify coverage gaps and sources of interference.
   - Ensure APs are centrally located, elevated, and away from obstructions like thick walls or metal objects.
   
   
2. Channel and Frequency Optimization:
   - Verify that the channels used by your APs are not overlapping and are set to non-congested channels. Use channels 1, 6, and 11 for 2.4 GHz and appropriate channels for 5 GHz.
   - Consider using the 5 GHz band more extensively, as it is less crowded and offers better performance.
   
   
3. Power Settings: Adjust the transmit power settings on your FortiAPs. Ensure that the 5 GHz band has a higher transmit power than the 2.4 GHz band to encourage clients to connect to it.
   
   
4. Interference Check: Check for non-Wi-Fi interference sources such as Bluetooth devices, microwaves, or cordless phones that might be affecting the signal.
   
   
5. Configuration Review: Review the FortiAP and FortiGate configurations to ensure they are optimized for your environment. This includes checking the AP profiles and ensuring features like band steering and frequency handoff are correctly configured.
   
   
6. Client Device Analysis: Analyze the client devices to ensure they support the latest Wi-Fi standards and are capable of connecting to the 5 GHz band.
   
   
7. Firmware and Updates: Ensure all devices, including FortiAPs and FortiGate, are running the latest firmware versions.
   
   
8. Load Balancing: Consider enabling load balancing features to distribute client connections evenly across available APs.

If the issue persists after these steps, it may be beneficial to engage with Fortinet support for a more detailed analysis of your specific setup and environment.