Study of the influence of human subject on the indoor channel using compact UWB directive/omni-directional antennas for wireless sensor network applications

This paper presents an investigation on the effect of human presence on the indoor channel for two different UWB antennas used as Tx-Rx nodes having directional and omni-directional characteristics. The position and direction of the human subject is varied along with the Tx-Rx nodes spacing (1-5 m) giving a complete overview of the indoor channel variation in the presence of the human subject. Various links such as LOS and NLOS are formed due to the change in the position/orientation of the human subject. Channel parameters such as path loss and rms delay spread are investigated for both the UWB antenna pairs and results indicate lower magnitude for the UWB Vivaldi antenna in comparison to UWB monopole antenna due to the directional nature of the Vivaldi antenna. The UWB human-presence detection capability is also explored and validated through experiments in an indoor environment. This is based on the variations caused in the channel links or the received signal due to the presence of the human subject which is compared with the scenario when the human subject is not present. The presence of the human subject significantly effects the indoor propagation channel and the performance of the wireless sensor network. The investigations and analysis carried out will be useful for security, detection, localization and tracking purposes.