What is DFS?

DFS is the abbreviation for Dynamic Frequency Selection, a wireless network technology used to automatically detect radar signals in the wireless spectrum and switch to other channels to avoid interference when these signals are detected. DFS is mainly applied in the 5GHz wireless band, especially in wireless networks using the 802.11a/n/ac/ax (Wi-Fi 5 and Wi-Fi 6) standards. The main purpose of DFS is to protect important radar services, such as military and weather radars, from interference by other wireless device operations. According to international and regional radio regulations, some channels within the 5GHz band are shared, meaning that Wi-Fi devices and radar systems may use the same frequencies. Therefore, Wi-Fi devices using DFS must have the capability to detect radar systems and automatically adjust their operating channels. In practical applications, when a Wi-Fi access point enables DFS, it listens to channels that may be allocated for Wi-Fi communication to detect if a radar system is in use. If a radar signal is detected, the DFS function will force the device to switch to another channel that will not cause interference, and the channel occupied by the radar will not be used again for a period of time. Currently, 5G WiFi products in the 5.25-5.35GHz and 5.47-5.725GHz bands require DFS testing in CE FCC, SRRC certification tests.