Interuser interference in adjacent wireless body area networks

The inter-user interference between wireless body area networks worn by two moving persons in an indoor environment at 60 GHz and 2.45 GHz is investigated experimentally. Both omni-directional antennas (monopoles) and directional antennas (horns) were used in the measurements. The interference power level variation and carrier-to-interference ratio were measured and characterized. Median interference power level reduction of nearly 20 dB was achieved in all measured channels by adopting 60 GHz radio transmissions compared to 2.45 GHz, both with omni-directional on-body antennas. A further 20 dB of interference level reduction was achieved at 60 GHz by adopting directional antennas confining the radiated wave along the body surface. Level crossing rates for interference power variation using omni-directional antennas range from 2.7–7.2 s⁻¹ at 2.45 GHz and 32–64 s⁻¹ at 60 GHz for static to progressively more dynamic links, whereas the corresponding range using 60 GHz directional antennas is reduced to 39–54 s⁻¹. The median improvement in the instantaneous carrier-to-interference ratio for the chest-head channel between 60 GHz and 2.45 GHz was approximately 30 dB. The measured interference power level and carrier-to-interference ratio, in dB, were found to satisfactorily fit the normal distribution according to the normalized root mean square error based fit metric.