The Duty Cycle Analysis for Electromagnetic Field Exposure From WLAN in a Busy Period

Duty cycle is a key factor for analyzing exposure to the electromagnetic field from the wireless local area network (WLAN). In this letter, we provide an analytical method for calculating the duty cycle of WLAN in a busy period. It relates to the medium access control (MAC) mode, durations of frames, and the random back-off time. We investigate the rate change rules for calculating the durations of control frames. These durations are also crucial to the parameter setting of the instrument in measurement. We propose a calculation method of the random back-off time for a common scenario, where retransmission always occurs due to collisions or interferences. The duty cycles and the average exposure levels are analyzed and compared between two MAC modes for different transmission rates. Our study can be applied to the extrapolation and the measurement of exposure to WLAN, and compliance testing with safety guidelines.