Study of Wireless Propagation for Body Area Networks Inside Space Suits

Future NASA plans include launching manned interplanetary missions to Mars and lunar destinations. These missions present new challenges that require rethinking of the extra-vehicular activity (EVA) suit design and associated communication systems. For example, there is a desire to collect more biomedical information from the astronaut to enhance safety and efficiency of EVA activities. Replacing the current wired biosensing within the suit with a wireless network would provide benefits such as the ability to monitor multiple vital signs and easily reconfigure the sensors to suit particular mission goals. In this paper, we study the propagation environment in a special domain of body area networks. In particular, within a space-suit where the outer cover-layer materials may be radio-opaque, containing the radio signals predominantly within the suit. This intrasuit wireless propagation environment is studied in various frequency bands, including 350 MHz, 433 MHz, 916 MHz, and 2.4 GHz, with signal attenuation used as the performance criterion. In all the frequencies studied, the intrasuit environment is shown to be conducive to wireless signal propagation, as the path loss is never more than 87 dB for a wide range of transmit-receive locations. Our findings suggest that ultrahigh frequency bands are the best candidate bands since there is interplay between the body conductivity favoring lower frequencies, and the difficulty of coupling RF energy into and out of the channel using suitably sized antennas favoring higher frequencies. The overall results suggest that deploying a wireless body area network inside the space suit is a promising solution for next generation missions.