Measurements and Analysis on Dynamic Off-Body Radio Channels at UWB Frequencies

This paper presents measurements on dynamic off-body radio channels in an ultra wideband frequency range for wireless body area network communications focusing on the human body shadowing effect. Measurements were conducted in an anechoic chamber at a bandwidth of 2-8 GHz by using a vector network analyzer. The investigation was performed at several discrete frequencies. Two planar prototype antennas were utilized (dipole and double loop). Six on-body antenna locations were applied and one off-body site. At first, ten frequencies were examined at two links, and the path loss values and standard deviations were determined. Second, all the links were considered at three discrete frequencies. The mean path losses varied between 47.6-69.4 dB, at human-pole distances on the average of 2m. The maximum recorded value was 101.7 dB. No clear difference was noted between the antennas. The usage of dipole and double loop as a link antenna pair has no remarkable effect compared to the case when all the antennas are similar.