Effect of environmental multipath on line of sight body to body communication at 2.45 GHz

Body to body links are the most scenario dependent form of body centric communications with performance highly dependent on the users' movements, relative positioning and the local operating environment. This paper focuses on line of sight cases which although they should be the most dependent, still have considerable variability depending on local propagation conditions. The results presented in the paper also raise important questions about the statistical characterisation of such links and the effect of different approaches to local mean averaging on fading characteristics. © 2012 IEEE.

Carrefours de la sociocritique. E´ dite´ par ANTHONY GLINOER. (¼ Texte: revue de critique et de the´orie litte´raire, 45/46). Toronto: E´ ditions Trintexte, 2009. 227 pp. Pb CAD $35.00

French Studies (2012) 66 (1): 125-126 doi:10.1093/fs/knr208

Received signal characteristics of outdoor body-to-body communications channels at 2.45 GHz

In this paper we conduct a number of experiments to assess the impact of typical human body movements on the signal characteristics of outdoor body-to-body communications channels using flexible patch antennas. A modified log-distance path loss model which accounts for body shadowing and signal fading due to small movements is used to model the measured data. For line of sight channels, in which both ends of the body-to-body link are stationary, the path loss exponent is close to that for free space, although the received signal is noticeably affected by involuntary or physiological-related movements of both persons. When one person moves to obstruct the direct signal path between nodes, attenuation by the person's body can be as great as 40 dB, with even greater variation observed due to fading. The effects of movements such as rotation, tilt, walking in line of sight and non-line of sight on body-to-body communications channels are also investigated in this study. © 2011 IEEE.

Shadowed fading in body–to–body communications channels in an outdoor environment at 2.45 GHz

In this paper a number of outdoor body-to-body communications channels at 2.45 GHz which are deemed to be susceptible to shadowed fading are analyzed. The newlyproposed shadowed K-Il model is used to characterize thesechannels. Its probability density function is shown to provide an improved fit to the distribution of the signal fading compared to established models such as lognormal, Nakagamiand Rice.

Small–scale fading characteristics of diversity combining schemes used for body–to–body communications within an urban environment at 2.45 GHz

In this paper, an analysis of spatial diversity and small-scale fading characteristics for body-to-bodycommunications is presented. The measurements were made at 2.45 GHz in an urban environment with uncontrolled pedestrian and vehicular traffic. The virtual array of four distributed receive antennas where situated on the centralchest, central waist, left waist and left wrist of the user’s body. Combining of the received signal measured at each ofthe antennas in the virtual array has shown that an average diversity gain of up to 11.8 dB can be achieved when usingfour distributed antennas and a maximal ratio combining scheme. To model the small-scale fading characteristics obtained at the output of the virtual combiners, we use diversity specific, theoretical probability density functions for multi-branch receivers operating in Nakagami-m fading channels. It is shown that these equations provide an excellent fit to the measured channel data.

Characteristics of shadowed fading in off–body communications channels at 2.45 GHz

In this paper, a number of off-body channels which are susceptible to shadowing caused by the human body are investigated. In particular, the recently proposed shadowed κ–μ fading model is fitted to data obtained from field trials performed in low multipath conditions at 2.45 GHz. It is shown that this model provides a significantly improved fit to off-body channels which are subject to shadowing when compared to other fading models such as lognormal, Nakagami-m and Rice which are commonly applied to model fading in body centric communications channels.

RSSI-based environment identification for 2.45 GHz body area networks

A unique property of body area networks (BANs) is the mobility of the network as the user moves freely around. This mobility represents a significant challenge for BANs, since, in order to operate efficiently, they need to be able to adapt to the changing propagation environment. A method is presented that allows BAN nodes to classify the current operating environment in terms of multipath conditions, based on received signal strength indicator values during normal packet transmissions. A controlled set of measurements was carried out to study the effect different environments inflict on on-body link signal strength in a 2.45 GHz BAN. The analysis shows that, by using two statistical parameters, gathered over a period of one second, BAN nodes can successfully classify the operating environment for over 90% of the time.