Co-Channel Interference in Body Area Networks with Indoor Measurements at 2.4 GHz: Distance-to-Interferer is a Poor Estimate of Received Interference Power

Inter-network interference is likely to be a significant source of difficulty for wireless body area networks. Movement, proximity of networks, the large number of nodes per network and the lack of central coordination make cellular approaches to interference modeling ineffective. We examine the interference power of multiple Body Area Networks (BANs) when people move randomly within an indoor office environment. The power-loss trend over 3 m is overwhelmed by random variations in the signal power. Distance-to-interferer is a poor estimate of instantaneous received interference power, and an even less reliable estimate of instantaneous signal-to-interference ratio (SIR). We develop a lognormal statistical model for the signal-to-interference which incorporates the distance effect.     

Temporal correlation of dynamic on-body area radio channel

Temporal autocorrelation of the dynamic on-body radio channel is characterised empirically and theoretically based on measurements. The channel coherence time is found to be approximately 20 to 70 ms for a human subject either walking or running. Using a Weibull distribution approximation to the channel taps there is a fair match between empirical and theoretical results for large correlation coefficients.     

First- and second-order statistical characterizations of the dynamic body area propagation channel of various bandwidths

Comprehensive statistical characterizations of the dynamic narrowband on-body area and on-body to off-body area channels are presented. These characterizations are based on real-time measurements of the time domain channel response at carrier frequencies near the 900- and 2,400-MHz industrial, scientific, and medical bands and at a carrier frequency near the 402-MHz medical implant communications band. We consider varying amounts of body movement, numerous transmit–receive pair locations on the human body, and various bandwidths. We also consider long periods, i.e., hours of everyday activity (predominantly indoor scenarios), for on-body channel characterization. Various adult human test subjects are used. It is shown, by applying the Akaike information criterion, that the Weibull and Gamma distributions generally fit agglomerates of received signal amplitude data and that in various individual cases the Lognormal distribution provides a good fit. We also characterize fade duration and fade depth with direct matching to second-order temporal statistics. These first- and second-order characterizations have important utility in the design and evaluation of body area communications systems.     

Volunteering: A Community Response to the Rena Oil Spill in New Zealand

We explore the experiences of people who volunteer to help remediate the effects of non‐natural environmental disasters. Following the grounding of the Rena, volunteers were engaged to clean up the resulting oil spill on the beaches of Tauranga, New Zealand. Volunteers were later invited to respond to an online questionnaire about their experiences. More women than men responded, and respondents tended to be older, and engaged in the paid workforce or retired. Greater membership in community organizations was associated with a greater participation in clean‐up events. Respondents were positive about the experience, and were more positive when they had actually participated in a clean‐up event, with positivity remaining high even after multiple volunteer occasions. Recommendations are made for increasing volunteer participation.     

Wireless communication systems with-spatial diversity: a volumetric model

This paper presents a novel physical-modeling approach to wireless systems with multiple antennas. The fundamental problem of modeling the communication channel is studied, where the channel consists of a finite spatial volume for transmitting, a finite spatial volume for reception, and an arbitrary set of reflective-scattering bodies. The number of communication modes (or degrees of freedom) for such a system is calculated, using the procedure developed. We present a simple model for multipath channels, which allows insight into the development of a correlated multiple-input multiple-output (MIMO) channel model. In particular, the model is independent of transmitter and receiver elements and relies on the physical parameters of the channel involved. Our work explains which physical parameters determine the channel model and its channel capacity.