On the one hand, the number of wireless personal devices (WPDs) owned by individuals has soared in the last five years. On the other hand, WPDs exposed their users to electromagnetic field (EMF) radiation that has been linked with possible adverse physiological effects. In this paper, we first provide a generic analytical framework for modelling the exposure generated by WPDs having two transmit antennas. Our model is based on reliable exposure data for different types of human dielectric properties; its accuracy is showcased via simulations. We then integrate this model in an optimization framework for minimizing the exposure, while meeting spectral efficiency (SE) requirements, by means of beamforming. Results show the existence of a trade-off between the specific absorption rate (SAR) and SE, such that our exposure minimization beamforming approach can reduce the exposure by at least 27% by trading-off only 1% of the SE when compared to the optimal SE-based beamforming approach. In addition, they also indicate that increasing the number of antennas at the receiver side can help to further reduce the exposure generated by WPDs.

Long haul transport can be considered an obvious deployment scenario for communication between vehicles travelling in convoy, where environments will be comparable to that of a rural highway. Therefore this paper addresses antenna array techniques applicable to such circumstances, which provide little scattering to the propagation channel and little support for diversity. Only beamforming is realistically suited to increase the capacity in the vehicle to vehicle link. However, the possibility to enable multi user channels is limited in such environments since the propagation channels are highly correlated when more than two vehicle to vehicle links are in close proximity. The deliberate introduction of delay spread through wide spaced and combined multiple antenna topology thus creating an artificial wideband fading channel is proposed in this paper, which results in de-correlated vehicle to vehicle links. Measurements and experimental results are presented that demonstrate the means by which uncorrelated wideband channels between separate vehicle to vehicle links can be formed to enable multi user capabilities specific to vehicles on a rural highway.

A novel, multi-slope dual breakpoint model for predicting path-loss in ultra-wideband (UWB) off-body communication channels, is proposed. This model is based on real-body measurements, carried out in the frequency range between 3.5GHz-6.5GHz, in an anechoic chamber. New parameters that describe this specific propagation environment are presented and evaluated. Results show that the first breakpoint point angle lies in the lit region of the transmitter and increases exponentially with distance until it rises to its threshold value. Based on this finding the near and far field areas for BAP (body to access point) channels are defined. In addition, newly estimated decay coefficients suggest severe degradation as the receiver moves in between the two critical angles. Finally, techniques for model expansion in two dimensions are discussed.

Preliminary results on the use of the vehicle to vehicle MIMO channel in a rural highway environment are presented. This is looked at both in terms of the available spatial multiplexing through singular value decomposition and also angular distribution within the channel. Results indicate a strong predominant line of sight link in general while instances of scattering from other vehicles will cause changes in the Doppler spectrum as well as beamforming jitter.