Electromagnetic environment in aircraft by wireless LAN system and its possibility of interference on avionics

This paper describes electromagnetic field distribution and strength in a Boeing 747-400 cabin by IEEE 802.11a/b/g LAN (WLAN). Emission from WLAN access point and terminal is measured first. Then, WLAN signal distribution is estimated by WLAN throughput distribution in the aircraft. WLAN signal level has been measured in several observation points when multiple access points and terminals are used simultaneously. The signal level is compared with the emission and susceptibility recommendations in RTCA DO-160D. Immunity of 32 avionic systems is examined in WLAN frequencies. The results show that the signal variation in the cabin becomes more than 10 dB. The signal level by multiple WLAN access points and terminals has been 15-30 dB higher than recommended emission limits of RTCA DO-160D Category M. And the peak level is as high as the susceptibility test level of DO-160D Category T. The immunity test has shown that no avionic systems under test demonstrate anomalies.