Oven. The most common source of interference in the ISM band is the microwave oven (MWO). Nearly every home, apartment, office, and restaurant in a large metropolitan area contains an MWO, and its operation can severely degrade WiFi transmission. Both residential and commercial MWOs are characterized by a wide-band frequency profile. However, the interference varies in time with a nearly even on-off cycle corresponding to its 60 Hz AC power supply. This corresponds to a period T of approximately 16.7 ms, a key characteristic used in both modeling and identifying MWO signals.