Andrea Sani

Transient Characteristics of Wearable Antennas and Radio Propagation Channels for Ultrawideband Body-Centric Wireless Communications

This paper presents transient characterization of ultrawideband (UWB) body-worn antennas and on-body radio propagation channels for body-centric wireless communications. A novel miniaturized CPW-fed tapered slot antenna is proposed and used for transient measurements of UWB radio channels for body area network (BAN) and personal area network (PAN) scenarios. Unlike conventional UWB CPW-fed antennas, the proposed antenna employs two diverging tapered slots to provide smooth and stable impedance matching. Fidelity analysis is applied to evaluate the time-domain behavior of body-worn antennas and it is found that average fidelity obtained is 88% and 86% for the conventional coplanar waveguide fed antenna and the tapered slot antenna, respectively. However, the tapered slot antenna shows a significant size reduction and hence is suited for body-centric wireless communications.

Antennas and Propagation of Implanted RFIDs for Pervasive Healthcare Applications

Radio-frequency identification (RFID) is a growing technology, with the potential for reducing medical errors and improving the quality of healthcare in hospitals. The benefits include more secure and safe access in the healthcare environment (with the possibility, for example, to track patients, personnel, and equipment), as well as providing the means to easily identify patients and their medications with low risk of error. In this paper, we present an overview of the challenges faced in antenna design, electromagnetic modeling and wave propagation for RFID implants. The performance of ultra-high-frequency (UHF) subcutaneous tag antennas was investigated numerically and validated with measurements. Furthermore, the wave propagation between an off-body reader and an implanted tag was analyzed, in both free space and a scattered indoor environment. Results demonstrated that a passive tag solution allows a very limited communication range, due to the body losses, the electrically small size of the antenna, and nulls in the radiation pattern. In comparison, a maximum communication range of 10 m was predicted as achievable for an active tag operating indoors with a limited power (-20 dBm).

Numerical Characterization and Link Budget Evaluation of Wireless Implants Considering Different Digital Human Phantoms

This paper presents a numerical investigation of the radiation characteristics of gastric, bladder, and cardiac implants based on the finite-differences time-domain method. Simulations were performed at the medical implanted communication services (MICS) and the industrial, scientific, and medical radio bands, respectively, using three different digital inhomogeneous human phantoms (two male and one female models). The numerical analysis demonstrated that the radiation performances are strongly dependant on the location of wireless implants, as well as the body mass index of the subject. The results highlighted the significance of subject specific modeling when designing wireless implants. A link budget calculation was proposed for the communication between a left-ventricular wireless implant and an off-body base station as an example for MICS applications. It is demonstrated that, due to the presence of human tissues, the antenna radiation from wireless implants tends to be directive, and therefore, the signal-to-noise ratio in communication links is strongly dependent on the orientation of the human subject with respect to the base station.

Experimental Characterization of UWB On-Body Radio Channel in Indoor Environment Considering Different Antennas

An experimental investigation to characterize the transient and spectral behavior of the ultrawideband (UWB) on-body radio propagation channel for body-centric wireless communications is presented. The measurements were performed considering over thirty on-body links in the front of human body in the anechoic chamber, and in indoor environment. Two different pairs of planar antennas have been used, namely, CPW-fed planar inverted cone antennas (PICA), and miniaturized CPW-fed tapered slot antennas (TSA). A path loss model is extracted from measured data, and a statistical study is performed on the time delay parameters. The goodness of different statistical models in fitting the root mean square (RMS) delay has been evaluated. Results demonstrate that the TSA, due to its more directive radiation behavior is less affected from the reflections from body parts and surrounding environment. The antenna shows significant size reduction and improved time delay behavior, and hence is an ideal candidate for UWB body area networks (BAN).

On-Body Radio Channel Characterization and System-Level Modeling for Multiband OFDM Ultra-Wideband Body-Centric Wireless Network

Given the trend towards a user-centric concept in mobile communications, body area networks have received increasing attention within the wireless personal and body area networks community. In this paper, an experimental investigation is presented to derive suitable radio propagation models for ultra wideband (UWB) body-centric wireless communications. The performance of the body-centric UWB radio channel is investigated by considering several on-body links, including different body postures. System-level modeling of potential multiband orthogonal frequency-division multiplexed UWB system has been conducted and system performance is measured using bit error rate (BER) and signal-to-noise ratio. The conducted system analysis demonstrated that for 78% in the static case and 75% and 61% for stable and unstable transmitter locations in the pseudodynamic in-motion scenarios (respectively) of the specified on-body radio links, the BER is equal to or less than 0.1%. This demonstrates promising applications of the proposed UWB body-centric radio system. Based on these results, clear recommendations are given for best on-body locations leading to optimal system performance.

Numerical Characterization and Modeling of Subject-Specific Ultrawideband Body-Centric Radio Channels and Systems for Healthcare Applications

The paper presents a subject-specific radio propagation study and system modeling in wireless body area networks using a simulation tool based on the parallel finite-difference time-domain technique. This technique is well suited to model the radio propagation around complex, inhomogeneous objects such as the human body. The impact of different digital phantoms in on-body radio channel and system performance was studied. Simulations were performed at the frequency of 3-10 GHz considering a typical hospital environment, and were validated by on-site measurements with reasonably good agreement. The analysis demonstrated that the characteristics of the on-body radio channel and system performance are subject-specific and are associated with human genders, height, and body mass index. Maximum variations of almost 18.51% are observed in path loss exponent due to change of subject, which gives variations of above 50% in system bit error rate performance. Therefore, careful consideration of subject-specific parameters are necessary for achieving energy efficient and reliable radio links and system performance for body-centric wireless network.

An Efficient FDTD Algorithm Based on the Equivalence Principle for Analyzing Onbody Antenna Performance

In this paper, on body antenna performance and its effect on the radio channel is analyzed. An efficient numerical technique based on the finite-difference time-domain technique and the equivalence principle is developed. The proposed technique begins with the problem decomposition by separately computing the wearable antennas and on body propagation involving the digital human phantom. The equivalence principle is used as an interface between the two computational domains. We apply this technique to analyze on body antenna and channel characteristics for three different planar body-worn antennas operating at the industrial-scientific-medical frequency band of 2.4 GHz. Simulated results are validated with measurement data with good agreement.

Arm movements effect on ultra wideband on-body propagation channels and radio systems

This paper presents experimental investigation of ultra wideband on-body radio channel in both the anechoic chamber and indoor environments including effects of time varying movements of various body parts on the the channel characteristics. Measured data are used to extract radio propagation channel parameters and investigate the influence of body movements on derived channel models. These models are applied in conjunction with different modulation techniques commonly used for impulse radios to evaluate the system performance of on-body UWB radio systems. Bit error rate and signal-to-noise ratio studies show that careful considerations need to be taken when choosing the modulation technique for optimal ultra wideband body-centric systems.

Modeling of path loss for ultrawide band body-centric wireless communications

This paper presents the characterization of the path loss in ultrawide band body area networks. A Measurement campaign was performed in the anechoic chamber and in an indoor environment for comparison. The propagation along the front part of the body was analyzed, and the effect of the body movements on the signal strength was investigated. The results demonstrated that the normal distribution provides the best fit for modeling the path loss.

Experimental Characterization and Statistical Analysis of the Pseudo-Dynamic Ultrawideband On-Body Radio Channel

This letter investigates the effect of body movements on the ultrawideband (UWB) on-body radio channel. A measurement campaign was performed considering four different body-links, namely: belt-to-head, belt-to-chest, belt-to-wrist, and belt-to-ankle, with the subject performing movements of different nature, in order to cover a wide range of scenarios. Transient and spectral characteristics were extracted from the measured channel data. The post-measurement analysis concluded that the normal distribution provides the best fitting for the path loss, while the root mean square delay is better modeled with a log-normal distribution. In addition to first-order statistics, this letter analyzes and discusses second-order channel parameters such as level crossing rate, average fade duration, and fade probability for the proposed on-body propagation links.