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 of rain on channel gain was analyzed and experimentally evaluated. A modified electric model of body channel was given and based on which the changing tendency of channel 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 of the body channel cover the frequency range from 100 kHz to 10 MHz. Wet sponge was used to emulate the changing of air 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 to frequency when user is barefoot. The higher the frequency is, the less effect of ambient humidity is. Accordingly, a carrier frequency higher than 1 MHz is recommended for rainy day application.