Resolving Wi-Fi Performance Issues Due to High Airtime Utilization

Having difficulty connecting to WiFi in various parts of your network? High airtime utilization may be the cause. When too many devices compete for the same channel, it can lead to slow speeds, dropped connections, and lag. This congestion is often caused by interference from nearby networks, interference within your own network, slow-transmitting devices, and excessive traffic from your own access point (AP). Understanding these factors and optimizing your network settings can help improve performance.

Identifying High Airtime Utilization

If you experience slow speeds, dropped connections, or increased latency, high airtime utilization may be the cause. This issue is more common in environments with a high concentration of devices or in densely populated areas.

To check airtime utilization:

1. Navigate to Radios > Performance in your AP’s settings.
2. Select an access point in the top left corner.
3. If the utilization bar is high, it might be related to degraded performance.
4. The color-coded breakdown indicates different sources of airtime usage. Which factor is driving high airtime utilization determines your course of action:
   • Blue represents your AP’s traffic (transmit and receive). If this is high, see Reducing AP Multicast Traffic, below.
     • Dark Blue shows RX (Receive)
     • Light Blue shows TX (Transmit)
   • Orange represents interference from other networks. If this is high, see Troubleshooting Network Interference, below.

Optimizing WiFi Performance

If high airtime utilization is affecting your network, consider the following optimizations.

Troubleshooting Network Interference

1. Verify Interference Source
   • If network interference is high (indicated by orange in the graph described above), it may be due to interference within your own network or from nearby networks.
2. Check Your AP Configuration
   • Ensure adjacent APs use different channels on 2.4 GHz, 5 GHz, and 6 GHz bands.
   • Consider using DFS channels on 5 GHz, which may be less congested.
     1. Note that APs may temporarily switch away from DFS channels for regulatory reasons (e.g., radar detection). For more on DFS channels, click here.
3. Investigate Other WiFi Networks
   • Navigate to Radios > Environment.
   • Select your AP from the drop-down menu in the top left.
   • View the frequency bands to assess congestion and identify any overlapping networks contributing to interference.
4. Conduct a Site Survey (If Needed)
   • In complex deployments, a professional site survey can help pinpoint the optimal channels.

For additional WiFi optimization tips, see this article.

Reducing AP Multicast Traffic

1. If Transmit / Receive traffic utilization is high (indicated by blue in the graph described in section 1), high multicast traffic may be a culprit
2. This issue is common in environments with significant mDNS Discovery traffic, where devices such as Chromecasts, Apple TVs, and Bonjour printers generate a lot of multicast data.
3. To reduce multicast traffic:
   • Go to Settings > WiFi, and click on an SSID to open it.
   • Turn on Multicast and Broadcast Control and add any exceptions (devices like printers, Airplay, or Chromecast).
     • Note that this may degrade the ability of devices to be discovered across different APs.
   • Adjust the Minimum Data Rate.
     • Devices transmitting at lower speeds consume more airtime; increasing the minimum data rate forces them to communicate faster, thereby reducing the airtime consumed by multicast and broadcast traffic (including DHCP).
     • Note that this setting may impact older or IoT devices that rely on lower data rates—for instance, devices based on 802.11b might lose connectivity.
4. In some cases, Multicast Enhancement may work as a step to reduce Multicast traffic with fewer impacts to device discoverability

Use APs with PRISM Technology in Outdoor Environments

• PRISM technology, available in E7-Campus and E7-Audience APs, enhances connectivity and throughput by applying advanced hardware filtering on the AP Rx antennas.
• This feature is especially useful in challenging outdoor WiFi environments where interference is more prevalent from adjacent channel APs. 
• PRISM filtering applies to 20/40/80 MHz channels in the UNII-2C and UNII-3 frequency ranges.