Recent progress of ultra wideband radio propagation studies for body area network

This paper reviews recent advances in ultra wideband (UWB) radio propagation measurements and modeling for wireless body area networks (WBAN) under a research project between Tokyo Denki University and National Institute of Information and Communications Technology of Japan. Several measurement campaigns and associated modeling have been carried out in either a radio anechoic chamber or a specific room type; however, dependence of the radio propagation on surrounding environments has not been studied. Multipaths (mainly reflected from floor, ceiling, and walls) depend particularly highly on the environment. Propagation measurements were carried out (including lower body sections) in three different surrounding environments: a radio anechoic chamber, a classroom, and a small room. The propagation losses of continuous wave (6.85 GHz), low-band UWB (3.4-4.8 GHz), and high-band UWB (7.25-10.25 GHz) were evaluated in comparison with that of full-band UWB (3.1-10.6 GHz). Parameters in a conventional propagation loss model were derived from the measured data. The parameters were found to significantly diverge and depend on room volume and body sections. A modified model considering the impact of the room volume has been proposed for individual body sections. Different propagation mechanisms were discussed along with the parameter derivation. Probability distributions for the UWB propagation loss and delay spreads were also examined.