Alessio Brizzi

Numerical Analysis and Characterization of THz Propagation Channel for Body-Centric Nano-Communications

This paper presents the characteristics of electromagnetic waves propagating inside human body at Terahertz frequencies and an initial study of the system performance of nano-network. It has been observed that the path loss is not only the function of distance and frequency but also related to the dielectric loss of human tissues. Numerical results have been compared with analytical studies and a good match has been found which validates the proposed numerical model. Based on the calculation of path losses and noise level for THz wave propagation, the channel capacity is studied to give an insight of future nano-communications within the human body. Results show that at the distance of millimeters, the capacity can reach as high as 100 Terabits per second (Tbps) depending on the environment and exciting pulse types.

A whole body statistical shape model for radio frequency simulation

The development of ultra low power wireless sensors for customized wearable and implantable medical devices requires patient specific models for radio frequency simulation to understand wave propagation in the body. In practice, the creation of a patient specific whole-body model is difficult and time consuming to create. It is therefore necessary to establish a method for studying a population in a statistical manner. In this paper, we present a statistical shape model for the whole body for RF simulation. It is built from 10 male and 10 female subjects of varying size and height. This model has the ability to instantiate a new surface mesh with the parameters allowed by the training set. This model would provide shapes of varying sizes for studies, without the requirement of obtaining subject specific whole body models. Results from finite-differences time-domain simulation are presented on the extreme shapes from the model and demonstrate the need for a full understanding of the range in body shapes.

Design of a cylindrical resonant cavity antenna for BAN applications at V band

An antenna for on-body applications based on a cylindrical resonator is presented in this paper. The antenna is designed to work at V-band, specifically in the unlicensed bandwidth around 60GHz.The resonant cavity is obtained by means of a woodpile Electronic Band Gap (EBG) structure made of alumina, and exhibits an omnidirectional radiation pattern on the plane normal to the cylinder axis. Such characteristic is extremely important for on-body application, since it improves the signal coverage of the human surface while reducing the energy lost in off-body radiation.

Quantitative Analysis of the Subject-Specific On-Body Propagation Channel Based on Statistically Created Models

This letter presents a quantitative approach to the investigation of subject-specific on-body communication channels. To this aim, propagation at 5.8 GHz has been studied considering 50 realistic digital phantoms, statistically generated from a set of 20 magnetic resonance (MR) scans. Both line-of-sight (LoS) and non-line-of-sight (NLoS) communication links have been taken into account. Mathematical expressions are proposed reflecting the correlation between body dimensions (specifically height and waist) and path-loss variation. Results show that linear fitting can be extrapolated between path-loss variations and body shape parameters. In-house parallel finite-difference time-domain (PFDTD) numerical method has been applied to carry out full-wave simulations on the 50 digital phantoms.

Numerical analysis of the communication channel path loss at the THz band inside the fat tissue

With the growth of the demand of smaller and smaller implantable devices, THz technologies becomes appealing for potential applications in Body Area Networks at nano-scale. As an essential part for understanding the in-body propagation at THz frequency numerical investigations are presented in this paper to simulate the absorption path loss of fat at THz frequency. The results of the proposed analysis suggest that a distance in the order of millimeter might be suitable to guarantee a communication link between nano-devices located in human tissues.

Analysis of on-body propagation at W band by using ray tracing model and measurements

The propagation between a transmitter (TX) and a receiver (RX) operating at 94 GHz, located in proximity of a human body, is investigated in this paper. The TX is positioned near the head and a line of RXs is located on the left shoulder. The high frequency method of ray tracing has been used to simulate these links. The simulated Path Loss (PL) has been compared to measured data. The agreement between simulations and measurements supports the possibility of using ray-based method to correctly predict the PL at millimeter wavelengths.

Statistical Path-Loss Model for On-Body Communications at 94 GHz

A great amount of work on antennas and propagation for body-centric wireless communication has been studied at frequencies up to X band; however, on-body radio propagation at millimeter/sub-millimeter wave frequencies still remains largely unexplored. This paper presents a study of on-body radio propagation at 94 GHz, particularly focusing on the analysis of specific channels such as waist-to-torso and head-to-shoulder links. Measured data are compared with results obtained with numerical simulations emphasizing the sensitivity of the simulated path loss to the positioning of the receivers with respect to the human body.

Numerical analysis of on-body channel for statistically-generated body shapes

The development of ultra low power wireless sensors for customized wearable medical devices requires patient specific information for the evaluation of the on-body communication channel. Direct measurements on human subjects are impractical for many applications. In such cases, numerical techniques for electromagnetic analysis, such as Finite Differences in Time Domain (FDTD), is an attractive alternative. To this end, it is necessary to create whole-body models that are representative to the population data. In this paper, RF simulation is performed on shapes generated from a range of subjects. A whole body statistical shape model is generated from twenty subjects of varying sizes and height. The simulations show the dependence of path loss on subject specific cases. The human models of higher size and higher curvature have greater path loss which is analogous to real cases, suggesting the practical value of the model. Five different extreme human body shapes obtained from the statistical models, and the results from FDTD simulations at 2.4 GHz are presented.

Investigation of the effect of fabric in on-body communication using Finite Difference Time Domain technique at 60GHz

An investigation of the effects of fabric over skin, evaluated in terms of transmission coefficient of a five layer model comprising of air-cloth-air-skin-air, is presented in this paper. The analysis is performed in the range of the millimeter waves at 60 GHz. The full wave numerical method Finite Differences Time Domain (FDTD) is used to analyze the investigated fabric-air-skin model. In order to avoid scattering from the edge, a two dimensional model has been considered and Periodic Boundary Conditions (PBC) have been imposed. The effect of varying depth of fabric causes change of transmission coefficient of skin from 10-18%. Results show the value of the transmission coefficient being strictly dependent on the thickness of both the fabric and the air gap between clothes and skin.

Experimental characterization of the propagation on the human torso at W band

Summary form only given. Interest in the use of millimeter wave frequencies for body-centric applications has been recently growing, also thanks to the advances in the realization of compact devices working at V and W bands. In addition, many potential benefits are connected to the presence of unlicensed portions of the spectrum around 60 GHz and 94 GHz, and the possibility of reaching data rates in the order of Gb/s (J. Wells, IEEE Microw. Mag., 3, 104-112, 2009). However, the use of millimeter waves for body-centric applications poses remarkable challenges, mainly relevant to the electrical dimensions of the human body and the dielectric properties of its constituent tissues. Moreover, the presence of clothing cannot be neglected, since their thickness is now comparable with the wavelength. Initial analyses of on-body propagation have already been carried out at 60 GHz and, in a more limited way, at 94 GHz highlighting the differences with the lower ISM and UWB frequencies. Nevertheless, further investigations are necessary in order to achieve a satisfactory characterization of the body-centric propagation channel at millimeter wave frequencies. To this aim, an experimental investigation of the path loss over the trunk of a human male together with a path loss model useful for link budget evaluation will be presented was carried out. The analysis has been performed at 94 GHz: a transmitter was placed on the left side of the waist of a human subject (representing a device attached to the belt), and the received signal was sampled over a grid of 143 points with a spacing of 3 cm. The minimum distance between transmitter and receiver was 10 cm, and the grid had dimensions 30 × 36 cm, thus covering the chest and the upper part of the abdomen. Different garments were considered, and the data from each set of measurements were analyzed in terms of path loss exponent and shadowing factor (T. S. Rappaport, Wireless Communications, Prentice-Hall, 102-106, 2001). This allowed to obtain path loss models useful for link budget and channel capacity evaluation. The measurement results and modeled parameters will be shown during the presentation, also highlighting how the different clothes worn by the subject affect the propagation over the torso.