Wireless Body Area Networks: Efficient Coexistence by Interference Management and Avoidance
Creators: name: Movassaghi, Samaneh
Publisher: name: The Australian National University
Year: 2020

description: Recent advancements in wireless communications, microelectromechanical systems (MEMS) and integrated circuits have enabled the development of low-power, intelligent, miniaturized sensors that can be placed strategically in, on, or around, the human body. The integration of these sensors in the form of a network is called wireless body area networks (WBANs). One key application of WBANs is in health monitoring to transport mission-critical and delay-sensitive data. Thus, a reliable WBAN needs to be highly immune to interference. Based on the IEEE 802.15.6 standard devised for WBANs, nodes in a single WBAN can avoid interference by using techniques such as time division multiple access (TDMA). In fact, the social nature of these networks and their high mobility highlights the importance of efficient communication between multiple WBANs that coexist with one another. Due to their mobility, it is generally not feasible to allocate a global coordinator. Moreover, with an increase in the number of WBANs that can coexist within close proximity of one another, communications can be severely degraded if interference avoidance is not taken into consideration. Thus, the primary goal of this dissertation is to devise new intelligent radio spectrum allocation strategies not only to avoid interference, but also to make best-use of the limited available spectrum for reliable communication in large-scale deployments. First, we introduce an adaptive and partially orthogonal scheme called Smart Spectrum Allocation (SCA), which allows synchronous and parallel transmissions between nodes in coexisting WBANs. This allows the practical coexistence of these networks with far less communication delay, higher throughput and less interference. A node’s traffic priority, packet length, received signal strength along with nnthe density of sensors within a WBAN are further incorporated in the SCA protocol to comply with real-world variations in terms of data type and message length. We later deploy an energy harvesting module for sensor radios in these networks and use the radio interference as a source of energy. Further, in order to better optimize resource allocation, a hybrid scheme incorporating graph-coloring with pair-wise clustering of coexisting WBANs is proposed. Next, in order to incorporate variations in channel assignment, based on bodydynamics mobility within each individual WBAN and amongst multiple WBANs, a prediction algorithm is proposed to feed in these dynamics and accordingly update resource allocation. This proposal maximises the resource usage and transmissionrate as well as offering a convenient trade-off between spectral reuse, transmission range and outage probability. Simulations and detailed analysis verify that the proposed approach is robust to variations in channel conditions, increase in sensor nodedensity within each WBAN, and an increase in the number of coexisting WBANs. Finally, we propose a self-organization scheme for the coexistence of multiple WBANs, which is biologically inspired from synchronization of fireflies in nature. This approach achieves distributed management of the available spectrum amongst coexisting WBANs, and avoids the need for global management. It allows coexisting WBANs to use delayed information from previous transmissions to adjust a collisionfree TDMA schedule, avoiding interference across WBANs, for future transmissions. Simulation results show that our protocol achieves rapid convergence to an updated spectrum allocation with higher packet delivery ratio, despite very-limited shared information from coexisting networks, implying that overhead is significantly reduced on WBANs with constrained resources.