Measures against shadowing problem on a bed using high-band UWB-BAN

We investigated the advantages and drawbacks of wireless body area network (BAN) systems using high-band ultra-wide band (UWB) wireless technology for healthcare. These systems are expected to have robustness against interference, low power consumption, and little interference from a human body. The most serious drawback is the shadowing problem due to a body in a hospital or home care bed. We confirmed by experiments and theoretical analysis that setting a coordinator near the ceiling and another coordinator under the bed is one of the best measures to prevent the shadowing problem. In this study, a shadowing model was used. A helical antenna having high antenna gain in the axial direction was used in the coordinator. In comparison with a biconical antenna, the helical antenna showed better radiation performance and less dependence on the angle direction of the antenna of the sensor node.