Comparison of duty cycle measurement techniques of 802.11b/g in the frequency and time domain

Medical device manufacturers are evermore including wireless communication in their medical devices. Because most utilize common wireless standards such as ZigBee and Bluetooth that operate in the unlicensed 2.4 GHz industrial, scientific, and medical (ISM) band, the Food and Drug Administration (FDA) is asking medical device manufacturers to test for wireless coexistence. Coexistence among wireless devices is dependent on three factors, namely frequency, space, and time. Specific to time, the probability of coexistence in the 2.4 GHz ISM depends on channel occupancy (or duty cycle) of the interfering wireless network-the main source being WiFi (802.11b/g) for ZigBee and Bluetooth. This paper reports on the implementation of two dutycycle measurement systems for 802.11b/g utilizing a National Instruments 5663E vector signal analyzer. Measurement techniques were designed in the frequency and time domain, and then compared. Simulations of 802.11b/g duty cycles were also executed and compared with experimental measurements.