Fading in Wearable Communications Channels and its Mitigation

The fabrication of miniature electronics and sensors has encouraged the creation of a wide range of wireless enabled devices designed to be worn on the human body. This has led to the prominence of so-called wearable communications, which have emerged to satisfy the demand for wireless connectivity between these devices and with external networks. The work in this thesis has focused on the characterization of the composite fading (i.e combined multipath and shadowing) observed in wearable communications channels. It has also investigated the mitigation of the deleterious effects of both of these propagation phenomena in wearable communications. In order to accurately characterize the behaviour of the composite fading signal observed in wearable communications channels, new fading models such as F, $\kappa$-$\mu$ / inverse gamma and $\eta$-$\mu$ / inverse gamma composite fading models, have been proposed. The generality and utility of these composite fading models have been validated through extensive field measurements performed in both indoor and outdoor environments with two key types of propagation geometry, i.e. line-of-sight (LOS) and non-LOS (NLOS) channel conditions. The potential improvement in signal reliability for wearable communications channels has been empirically investigated using a switched combining based micro-diversity setup (to mitigate multipath) and a switched combining based macro-diversity configuration (to overcome shadowing). Three different switched combining schemes are considered, namely switch-and-stay combining (SSC switch-and-examine combining (SEC) and SEC with post-examining selection (SECps). The output of each switched combining scheme is also statistically characterized using diversity specic analytical equations. To mitigate occurrences of simultaneous multipath and shadowing, the signal reliability improvement which can be achieved when using dual-stage micro- and macro-diversity based combining has also been investigated through field measurements conducted in both indoor and outdoor environments.