Spatial diversity for off-body communications in an indoor populated environment at 5.8 GHz

Human activity in the vicinity of body-centric wireless communications systems often affects received signal characteristics. In particular, pedestrian movements may induce temporal fading and cause shadowing events in situations where an individual or group obstructs the dominant signal path. In this paper, we report results from a series of carefully controlled experiments aimed at assessing the impact of using multiple-antenna techniques to reduce the influence of pedestrian effects on off-body radio-links. Using two co-located, spatially-separated bodyworn antennas mounted on the anterior human torso, it was found that the cross-correlation coefficient value between branches was always less than 0.7, irrespective of the number of nearby pedestrians. The difference in mean signal level between receiver branches generally decreased as pedestrian numbers increased. Post-detection selection combining of the measurement data has shown that diversity gain improves with increased human traffic in the local environment.