UHF-radio propagation predictor for temporal variations in populated indoor environments

Ray-tracing is often used for site-specific propagation predictions, but current methods generally fail to accommodate shadowing and reflections caused by the movement of people: these represent significant effects in indoor radio environments. The method presented here improves site-specific indoor propagation predictions by including multiple, moving human bodies. The model, based on a hybrid image and ray-shooting approach, alto takes into account electromagnetic antenna-tissue interaction for body-worn terminals found in personal communications applications. The signal fading caused by pedestrians is demonstrated through simulations of a small-area (150 m2) open-plan office environment at 2.45 GHz. For a fixed point-to-point link, temporal variations in the received signal were observed over a wide range of ∼38dB and were caused solely by the movement of pedestrians. The situation becomes worse when a mobile terminal is considered: a ∼58dB variation in received signal power was observed. This variation was caused by combination of three distinct effects: spatial fading, temporal variations and antenna-body interaction. It was noted that, for antennas in close proximity to the user’s body (as may be found in personal applications using technology such as Bluetooth), a reduction in average received power of 15 dB occurred, directly due to antenna-body interaction.