An Experimental Investigation into the Impact of Vehicular Traffic on Interpersonal Wearable-to-Wearable Communications Channels

In this paper, we have investigated the effects of vehicular traffic on interpersonal wearable-to-wearable (W2W) communications channels in an urban environment at 2.45 GHz. In particular, we have studied the perturbations in the received signal caused by different types of vehicles as they passed through a channel between two persons who maintained various relative orientations while positioned at the opposite sides of a road. As the channel underwent different fading mechanisms depending on whether the vehicle was approaching, transitioning (i.e., intersecting the direct signal path), or receding from the persons, the overall disturbance was appropriately segmented depending on the journey stage. The results have shown that relative body orientation was a significant factor when considering the impact that a vehicle can have on a W2W link. When both persons faced the oncoming traffic, the link was particularly susceptible to significant fading events with variations in the received signal power from the unperturbed state as great as 44.1 dB observed to occur. For all of the journey stages, irrespective of the relative orientation of the persons, the logarithmically transformed long-term fading process was found to be multimodal and well described by a Gaussian mixture model. During the transitioning phase, shadowing caused by the passing automobile obstructing the line-of-sight signal path was found to be the main contributor to the signal fading. However, probably the most remarkable result of the channel characterization work conducted in this paper was the severity of the short-term fading often observed. Such was the intensity of the measured envelope fluctuation in many of the scenarios, we have been able to utilize the recently proposed κ - μ extreme distribution with great success and in the process, provide a further important empirical validation of this new fading model. Moreover, we have used the resistor-average distance, which is derived from the Kullback-Leibler distance to show the improved fit that the κ - μ extreme distribution offers compared with the κ - μ distribution when used to model the W2W channel in this fading environment.</p

Pedestrian-to-Vehicle Communications in an Urban Environment: Channel Measurements and Modeling

As wireless connectivity becomes increasingly ubiquitous, a greater emphasis will be placed upon the seamless integration of dissimilar networking technologies. One such example of this will occur in urban environments, where wearable devices and vehicular networks will operate in close proximity to one another. Clearly, a natural extension to both types of network is their interconnectivity through vehicle-to-pedestrian (V2P) or equivalently pedestrian-to-vehicle (P2V) communications as part of a much greater vehicle-to-X (V2X) based Intelligent Transportation System (ITS). To this end, we empirically investigate the P2V communications channel at 5.8 GHz for the case of a moving vehicle when a person positioned by the edge of a road was either stationary or walking parallel to the side of the highway. The measurements considered a chest mounted transmitter and four receiver locations on the vehicle covering the front wing mirrors and two positions on the roof, which simultaneously recorded the received signal power. To characterize the propagation mechanisms which are responsible for shaping the received signal in the P2V channel we decomposed it into its path loss, large-scale and small-scale fading components. We first show that although there was evidence of interference caused by multiple rays interacting with one another, the popular Two- Ray ground-reflection path loss model was unable to adequately describe the compounded effects of the vehicle and pedestrian’s body on the signal attenuation in the majority of the considered scenarios. Instead, we found that the overall path loss was well characterized using a dual-slope log-distance model, with lognormal large-scale fading. Due to the often severe small-scale fading that was observed in the P2V channel, we have been able to utilize the kappa-mu Extreme distribution with considerable success to characterize the worse than Rayleigh fading conditions which were encountered