Network-integrated sensing and energy-aware protocols in wireless body area networks

The objective of this thesis is to develop an end-to-end framework for network integrated sensing and energy-aware protocols for supporting applications in resource-constrained Wireless Body Area Networks (WBAN). A large number of existing WBAN applications involving physical activity monitoring and body posture detection use multi-axis accelerometry as the primary sensing modality. While the accelerometer-based approaches work well for identifying high-activity postures such as walking and running, they do not work well when it is necessary to differentiate between low-activity postures such as standing, sitting, lying down, and sometimes with finer granularity such as sitting upright or reclining. The key contribution of the first part of this thesis is to develop a novel network-integrated sensing modality, inter-sensor relative proximity, which is inferred from the measured Received Signal Strength Indicator (RSSI) of the Radio Frequency (RF) signal between each pair of WBAN sensors. The concept of RSSI-based proximity is experimentally developed and then integrated within a Hidden Markov Model (HMM)-based stochastic processing framework for accurately identifying human body postures in a subject-independent manner.In the second part of the thesis, the issue of energy-aware on-body communication is addressed by developing a human body posture-aware transmission power control framework. A closed loop link power assignment framework has been developed in which the RF power on an on-body network link is dynamically adjusted depending on the instantaneous postural orientation of a subject individual. It was demonstrated that such posture-aware mechanisms can outperform the traditional power control algorithms by leveraging on-body RF attenuation information which heavily depends on postural configurations.In the third part of this thesis, an on-body Delay Tolerant Network (DTN) routing framework has been developed. Ultra-short transmission range is a common constraint for low-power RF transceivers used for embedded applications with limited energy and small form-factors. For such ultra-short transmission range, postural body movements can make the WBANs to be highly prone to topological partitioning, resulting in a body area Delay Tolerant Network (DTN). Such topological partitioning can often get aggravated by the unpredictable on-body RF attenuation. The objective of this part of the thesis was to develop on-body store-and-forward packet routing algorithms, along with an analytical framework for modeling routing delay in the presence of network partitioning. The goal is to minimize end-to-end packet delay while minimizing the end-to-end hop-count, so that the transmission energy drainage is minimized.