Interuser Interference in Adjacent Wireless Body Area Networks

The interuser interference between wireless body area networks worn by two moving persons in an indoor environment at 60 and 2.45 GHz is experimentally investigated. Both omnidirectional antennas (monopoles) and directional antennas (horns) were used in the measurements. The interference power-level variation and carrier-to-interference ratio (CIR) 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 omnidirectional 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 omnidirectional antennas range from 2.7 to 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 CIR for the chest-head channel between 60 and 2.45 GHz was approximately 30 dB. The measured interference power level and CIR, in dB, were found to satisfactorily fit the normal distribution according to the normalized root-mean-square error-based fit metric.