1. Introduction: The Regulatory Tightrope In the unlicensed 5 GHz band, Wi-Fi shares spectrum with critical infrastructure—namely, Terminal Doppler Weather Radar (TDWR) and military surveillance systems. To prevent interference, regulatory bodies (FCC, ETSI, MIC) mandate Dynamic Frequency Selection (DFS) . When a Wi-Fi Access Point (AP) operating on a DFS channel detects a radar pulse, it must vacate that channel within a strict timeline (e.g., 10 seconds) and avoid reusing it for a non-occupancy period (e.g., 30 minutes).
Example automation script:
[FW_DBG] radar_seq: 12 pulses, avg_PRI 413us, min_PW 1.2us, max_PW 2.1us [FW_DBG] correlation: 85% match to ETSI Type_3 (Weather Radar) If you see correlation: 0% but radar_event=1 , you likely have a —a common issue with low-cost LNAs that saturate near GSM towers. 5. Real-World Workflow: Debugging a DFS "Channel Hopping" Issue Symptom: An AP on channel 120 switches to 36 every few minutes, despite no radar being present.
1. Introduction: The Regulatory Tightrope In the unlicensed 5 GHz band, Wi-Fi shares spectrum with critical infrastructure—namely, Terminal Doppler Weather Radar (TDWR) and military surveillance systems. To prevent interference, regulatory bodies (FCC, ETSI, MIC) mandate Dynamic Frequency Selection (DFS) . When a Wi-Fi Access Point (AP) operating on a DFS channel detects a radar pulse, it must vacate that channel within a strict timeline (e.g., 10 seconds) and avoid reusing it for a non-occupancy period (e.g., 30 minutes).
Example automation script:
[FW_DBG] radar_seq: 12 pulses, avg_PRI 413us, min_PW 1.2us, max_PW 2.1us [FW_DBG] correlation: 85% match to ETSI Type_3 (Weather Radar) If you see correlation: 0% but radar_event=1 , you likely have a —a common issue with low-cost LNAs that saturate near GSM towers. 5. Real-World Workflow: Debugging a DFS "Channel Hopping" Issue Symptom: An AP on channel 120 switches to 36 every few minutes, despite no radar being present.