Experiments on WLAN Interference Reduction by Dynamic Frequency Selection in C-Band Weather Radars

We present experiments on interference in C-band weather radars conducted in the PREVENIR project between Argentina and Japan, supported by Science and Technology Research Partnership for Sustainable Development (SATREPS) in collaboration between Japan Science and Technology Agency (JST, JPMJSA2109) and Japan International Cooperation Agency (JICA). C-band weather radars in Argentina receive interference from urban wireless LANs (WLANs), which leads to inaccurate weather observations. Argentina's radars use the 5.6 GHz frequency band, while WLANs using the 5.6 GHz frequency band are required to have a mechanism, called the dynamic frequency selection (DFS), to avoid interference with weather radars. In DFS, when a WLAN detects a particular pulse pattern, the frequency used by the WLAN is changed to avoid the interference. The DFS pulse patterns depend on the country or region, but usually follow either the patterns defined by the Federal Communications Commission (FCC) or the European Telecommunications Standards Institute (ETSI). On a sunny day without clouds, we had a radar in Buenos Aires, Argentina transmit pulse patterns that satisfied both specifications of FCC and ETSI, and we investigated whether the received signal power changed or not before and after the pulse transmission. From the experimental results, we confirmed that the received signal power was greatly reduced while transmitting the DFS pulse patterns, but the WLAN interference returned within 10 minutes after stopping the pulse transmission.