Preliminary study of rain effect on channel gain of body area communication

Body area communication could be a promising solution of next generation wearable networks for pervasive computing. The effect ofrain on channel gain was analyzed and experimentally evaluated. A modified electric model ofbody channel was given and based on which the changing tendency ofchannel gain was studied. In rainy day, capacitances and resistances in the electric model will vary, which leads to the change of channel gain. Analysis results show that channel gain increases moderately with the capacitance between human body and transmit electrode or receive electrode, and decreases with the capacitance between human body and transmitter suspension ground or earth ground. The measurements ofthe body channel cover the frequency range from 100 kHz to 10MHz. Wet sponge was used to emulate the changing ofair and clothes humidity. Results show that wet sponge brings perceptible change to received signal amplitude, which is in accord with the analysis result. Finally, channel gain was measured on wet lawn after rain. Results when barefoot and wearing shoes were compared as well as indoor trial. Channel gain is closely related tofrequency when user is barefoot. The higher the frequency is, the less effect of ambient humidity is. Accordingly, a carrierfrequency higher than IMHz is recommendedfor rainy day application.