Off-body wireless link simulation framework using deterministic channel modeling

Body-centric communication concerns wireless links in which the human body represents the central element, exchanging data by means of wearable antennas with a different node in the external environment or on the human body itself. During the link design phase, it is very advantageous to be able to model the link and predict its performance before its real implementation, resulting in reduction of design time and costs. In the present contribution, we propose a novel computer simulation framework to describe a complete off-body communication link between a human user and a remote base station, including all the components of the communication link such as wearable and fixed antennas, human body and propagation channel at the physical level, also taking into account the digital data transmission at link level. The proposed framework was constructed by applying the most appropriate modeling tools for each component, including ray tracing for the deterministic channel modeling. The framework provides as output the most common link performance parameters such as Bit-Error-Rate (BER), received Signal-to-Noise Ratio (SNR) and channel correlations. The validity of the proposed method was verified by comparing the figures of merit of a real off-body communication link, studied during a previous measurement campaign, with the ones obtained by the proposed simulation framework. A good agreement is obtained in terms of both BERs and SNRs

Patch antenna with slanted ±45° dual polarization and performance comparison with H/V diversity

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Cylindrically-bent rectangular patch antennas: novel modeling techniques for resonance frequency variation and uncertainty

Wearable textile antennas are basic components in body-centric communication systems. Flexible wearable patch antennas, when integrated into a body-worn garment are subjected to bending, causing variation in the resonance frequency when compared to the flat-antenna. Bending conditions vary statistically among different human subjects. Therefore, it is very important to be able to predict performance variations due to bending. We propose novel models which allow to predict the deterministic and statistical variation in resonance frequency of rectangular wearable patch antennas. They consist of an analytical model for cylindrical-rectangular patch antennas, expressing resonance frequency as a function of the bending radius, and a novel technique based on polynomial chaos, that quantifies statistically the variations of the resonance frequency under randomly varying bending conditions. The proposed models have been experimentally and numerically verified, and proven to be much faster and computationally less expensive than traditional techniques based on EM solvers and Monte Carlo simulations, making them very advantageous tools for the design and characterization of body-worn patch antennas

An efficient technique based on polynomial chaos to model the uncertainty in the resonance frequency of textile antennas due to bending

The generalized polynomial chaos theory is combined with a dedicated cavity model for curved textile antennas to statistically quantify variations in the antenna's resonance frequency under randomly varying bending conditions. The nonintrusive stochastic method solves the dispersion relation for the resonance frequencies of a set of radius of curvature realizations corresponding to the Gauss quadrature points belonging to the orthogonal polynomials having the probability density function of the random variable as a weighting function. The formalism is applied to different distributions for the radius of curvature, either using a priori known or on-the-fly constructed sets of orthogonal polynomials. Numerical and experimental validation shows that the new approach is at least as accurate as Monte Carlo simulations while being at least 100 times faster. This makes the method especially suited as a design tool to account for performance variability when textile antennas are deployed on persons with varying body morphology

Diversity textile antenna systems for firefighters

Off-body communication systems are valuable to improve the security of rescue workers by allowing them to transmit vital information collected by sensors. As rescue workers often work in indoor environments characterized by many obstructions, non line-of-sight propagation with multipath effects and shadowing compromises the performance of the wireless communication. The reliability is enhanced drastically by the use of diversity techniques. In the measurement campaign presented, the performance of such an off-body diversity system is compared for two antenna configurations: two dual-polarized antennas, versus four circularly polarized antennas. The actual data transmission confirms the marginal difference between the two configurations, suggesting the use of dual-polarized systems for reasons of user convenience and ease of practical implementation