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In this paper, an analysis of radio channel characteristics for single- and multiple-antenna bodyworn systems for use in body-to-body communications is presented. The work was based on an extensive measurement campaign conducted at 2.45 GHz representative of an indoor sweep and search scenario for fire and rescue personnel. Using maximum-likelihood estimation in conjunction with the Akaike information criterion (AIC), five candidate probability distributions were investigated and from these the κ - μ distribution was found to best describe small-scale fading observed in the body-to-body channels. Additional channel parameters such as autocorrelation and the cross-correlation coefficient between fading signal envelopes were also analyzed. Low cross correlation and small differences in mean signal levels between potential dual-branch diversity receivers suggested that the prospect of successfully implementing diversity in this type application is extremely good. Moreover, using selection combination, maximal ratio, and equal gain combining, up to 8.69-dB diversity gain can be made available when four spatially separated antennas are used at the receiver. Additional improvements in the combined envelopes through lower level crossing rates and fade durations at low signal levels were also observed. [ABSTRACT FROM AUTHOR]

Biotelemetric systems, especially those that employ implanted devices, work with inductive links, where usually large circular external coils are separated by relatively large distances (dimensions of centimeters) from the small/Millimeter- or submillimeter-size) implanted coils. This paper shows that order these conditions, a simplified method for calculation of the mutual (M) between the coils, avoiding elliptic integrals, can be obtained. A procedure for coil design, with maximum M between them, is also described. [ABSTRACT FROM AUTHOR]

We report the experimental in situ characterization of 30-40 MHz and 868 MHz wireless transmission schemes for ingestible capsules, in porcine carcasses. This includes a detailed study of the performance of a magnetically coupled near-field very high-frequency (VHF) transmission scheme that requires only one eighth of the volume and one quarter of the power consumption of existing 868-MHz solutions. Our in situ measurements tested the performance of four different capsules specially constructed for this study (two variants of each transmission scheme), in two scenarios. One mimicked the performance of a body-worn receiving coil, while the other allowed the characterization of the direction-dependent signal attenuation due to losses in the surrounding tissue. We found that the magnetically coupled near-field VHF telemetry scheme presents an attractive option for future, miniturized ingestible capsules for medical applications. [ABSTRACT FROM AUTHOR]