Wireless Links for Telecare and Telemedicine Applications using Compact Body-Worn Antennas.

Abstract

This thesis concerns the design of body-centric wireless communications for short-range indoor Telecare/Telemedicine applications. Such communications are starting to be used to convey key, relatively low data-rate body-sensor data wirelessly between on-body sensor node(s) located on potentially mobile clients/patients and fixed off-body Access Point(s). From the outset, key practical considerations/constraints were assumed; in particular that, wherever possible, existing components (including antennas) and established protocols would be employed. This approach should enable existing manufacturers of mobile wireless components to rapidly adapt to the potential Telecare/Telemedicine market segment with minimum R&D capital outlay. In addition, maximum user convenience of the on-body nodes has been taken into account to ensure that they are readily accepted and hence actually used. As anticipated, using existing mobile antennas (designed for nominally free space use) in close proximity to the human body poses several limitations. These are quantified here for a particular candidate commercial device. In the process, however, a novel unanticipated effect of the nearby body was also discovered; namely that the body completely depolarises the (otherwise reasonably polarised) antenna patterns. A potential physical explanation for this effect is identified and evaluated by means of analysis based on a modified Geometric Optics approach. The result of this analysis agrees with those simulated and measured here to remarkable accuracy. The thesis then presents several multi-antenna schemes to overcome these severe limitations and identifies that best suited to the indoor Telecare/Telecommunication application here. Simulations at the Physical Layer are reported with this optimum Wireless Links for Telecare and Telemedicine using Compact Body-Worn Antennas 8 single-input multiple-output (SIMO) antenna scheme for a typical indoor scenario. These quantify the overall system performance when such measures are adopted, demonstrating that it is adequate in this role. Finally, promising techniques are suggested for Future Work which could afford further significant system improvements for future upgrades of the solution presented here. In particular, the use of metamaterial techniques are indicated which could substantially reduce on-body transmit powers currently required. This would give highly desirable increases in battery lifetimes for the mobile battery powered on-body nodes.