What is DFS?

Dynamic Frequency Selection (DFS) is a regulatory requirement that allows WiFi networks to share spectrum with critical radar systems, including weather radar, military radar, and aviation systems. WiFi access points (APs) operating on DFS-mandated channels must detect radar activity and switch channels if necessary.

DFS affects both indoor and outdoor WiFi deployments, but the exact rules differ depending on the regulatory domain. For the purposes of this document, rules from the United States will be used as examples. While the 5 GHz spectrum structure is globally similar, the allowed channels and conditions vary country by country. While Alta Labs abides by regulatory requirements, it is ultimately the operator's responsibility to ensure conformity to the relevant regulatory rules.

DFS and Non-DFS Channels in the 5 GHz Band

The 5 GHz spectrum is divided into groups of channels, with some requiring DFS and others exempt:

• Non-DFS Channels (widely usable by 5 GHz-capable devices)
  • 36 (5180 MHz), 40 (5200 MHz), 44 (5220 MHz), 48 (5240 MHz)
    (Range: 5150–5250 MHz)
  • 149 (5745 MHz), 153 (5765 MHz), 157 (5785 MHz), 161 (5805 MHz), 165 (5825 MHz)
    (Range: 5725–5850 MHz, with domain-specific limits)
• DFS-Mandated Channels
  • 52 (5260 MHz), 56 (5280 MHz), 60 (5300 MHz), 64 (5320 MHz)
    (Range: 5250–5350 MHz)
  • 100 (5500 MHz) through 144 (5720 MHz)
    (Range: 5470–5725 MHz)

Routers and APs must scan for radar before enabling DFS channels, and must immediately vacate if radar is detected.

Note: Different regulatory domains may restrict which of these channels are available indoors, outdoors, or at specific power levels. Always check your local regulations before deploying WiFi equipment. Alta Labs devices will geolocate themselves as they come online to ensure that they follow local regulations.

Pros of Using DFS Channels

1. Expanded Spectrum Access – DFS adds many more channels, easing congestion.
2. Higher Throughput Potential – Wider channels (80/160/320 MHz) are more feasible.
3. Reduced Congestion – Fewer consumer routers default here, so less crowded.
    

Cons of Using DFS Channels

1. Radar Avoidance Delays – APs must scan before transmitting, slowing startup. The wait time is typically 1 minute, but can last up to 10 minutes outside of the US.
2. Service Interruptions – Radar detection forces channel changes mid-operation.
3. Compatibility Gaps – Not all 5 GHz-capable devices support all DFS channels.
4. Outdoor Limitations – Some regions forbid DFS use outdoors.

Succinct Comparison of DFS vs Non-DFS Channels

• DFS Channels (52–64, 100–144)
  • Pros: More spectrum, less crowded, higher capacity.
  • Cons: Regulatory complexity, radar checks, limited device support.
• Non-DFS Channels (36–48, 149–165)
  • Pros: Broad support among 5 GHz devices, stable, no radar detection.
  • Cons: Fewer available, often crowded.

How Does DFS Affect My Alta Network

By default, there is no impact on your network.  Our Auto algorithm does not include DFS channels by default, due to the cons listed above.

You can allow DFS channels to be part of the Auto algorithm by going to Settings > System > Expand Advanced > Toggle On “5 GHz Auto Channel DFS”
 

You may optionally choose DFS channels (or any other channels) to exclude. By excluding channels, you ensure that the AP(s) will not use the specified channels as the center channel.  This is a critical note because if you’re using anything beyond 20MHz wide channels, the transmissions will overlap. For example, in the screenshot below, channel 132 is excluded, but channel 136 is not. Channel 136 @ 40MHz or bigger channel width has the potential to cross into channel 132.

Additionally, you can choose DFS channels for each individual AP if you opt not to use our Auto algorithm.

Conclusion

DFS channels are essential for scaling WiFi capacity, but they come with regulatory and technical challenges. Different regions enforce different rules: some channels are outdoor-permitted in one country but indoor-only in another.

For indoor deployments, DFS can provide significant performance improvements where client support exists. For outdoor networks, careful attention to local rules is critical, and non-DFS bands like 36–48 (5150–5250 MHz) or 149–165 (5725–5850 MHz) often serve as the universal baseline.

In short: DFS expands speed and capacity, with minimal risk. Non-DFS offers reliability across all 5 GHz devices, at the cost of limited spectrum.