How does radar detection and DFS affect system operation?

In regions where protection of radars is part of the local regulations, the ePMP must detect interference from radar-like systems and avoid co-channel operation with these systems.

To meet this requirement, the ePMP implements the following features:

  • The equipment can only transmit on available channels, of which there are none at initial power up. The radar detection algorithm will always scan a usable channel for 60 seconds for radar interference before making the channel an available channel.
  • This compulsory channel scan will mean that there is at least 60 seconds service outage every time radar is detected and that the installation time is extended by at least 60 seconds even if there is found to be no radar on the channel

There is a secondary requirement for bands requiring radar avoidance. Regulators have mandated that products provide a uniform loading of the spectrum across all devices. In general, this prevents operation with fixed frequency allocations. However:

  • ETSI regulations do allow frequency planning of networks (as that has the same effect of spreading the load across the spectrum).
  • The FCC does allow channels to be avoided if there is actually interference on them.

Please Note:
When operating in a region which requires DFS (Dynamic Frequency Selection), ensure that the AP is configured with alternate frequencies and that the SM is configured to scan for these frequencies to avoid long outages.  For more information on configuring these alternate frequencies, see ePMP Scanning AP List & DFS Alternative Frequency Configuration 

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