Field-Based Optimal Placement of Antennas for Body-Worn Wireless Sensors

Abstract

We investigate a case of automated energy-budget-aware optimization of the physical position of nodes (sensors) in a Wireless Body Area Network (WBAN). This problem has not been presented in the literature yet, as opposed to antenna and routing optimization, which are relatively well-addressed. In our research, which was inspired by a safety-critical application for firefighters, the sensor network consists of three nodes located on the human body. The nodes communicate over a radio link operating in the 2.4 GHz or 5.8 GHz ISM frequency band. Two sensors have a fixed location: one on the head (earlobe pulse oximetry) and one on the arm (with accelerometers, temperature and humidity sensors, and a GPS receiver), while the position of the third sensor can be adjusted within a predefined region on the wearer’s chest. The path loss between each node pair strongly depends on the location of the nodes and is difficult to predict without performing a full-wave electromagnetic simulation. Our optimization scheme employs evolutionary computing. The novelty of our approach lies not only in the formulation of the problem but also in linking a fully automated optimization procedure with an electromagnetic simulator and a simplified human body model. This combination turns out to be a computationally effective solution, which, depending on the initial placement, has a potential to improve performance of our example sensor network setup by up to about 20 dB with respect to the path loss between selected nodes.

Multi-Objective Optimization of a Wireless Body Area Network for Varying Body Positions

“…The paper presents a different and more advanced approach in comparison to our previous work [ 8 ], in which we imposed a number of limiting design assumptions—for example, fixed positions for the head and arm nodes. The only degree of freedom was the placement of the chest node.…”

Analysis of Human Body Shadowing Effect on Wireless Sensor Networks Operating in the 2.4 GHz Band

“…Cylinder-based models of the human body presented in the literature [ 39 , 40 , 41 ] show that this geometrical figure is adequate for both simulations and measurements of the interactions between a human body and electromagnetic waves. In previous work by the author [ 25 ], a dielectric cylinder-based model of the human body was successfully applied in the XGtd™ program to simulate the body-shadowing effect in the 3.6 GHz band.…”

“…Its relative electric permittivity was ε = 52, and its specific conductance was σ = 1.8 S/m. Those values of material parameters were also successfully used by the author for simplified numerical models of the human body in the FDTD method [ 40 , 41 ]. The simulations were performed in a free space environment, assuming that the only obstacle between the dipole antennas was the human body model.…”

Synthesis of Coupling Matrix for Diplexers Based on a Self-Adaptive Differential Evolution Algorithm

“…Due to such strong supporting information, the optimization algorithm does not need to be strong. At present, the widely used methods are general purpose optimization methods, such as Nelder-Mead simplex method [19], sequential quadratic programming [20], and evolutionary algorithms (EAs), which are widely used in microwave engineering [21]- [24].…”