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Automated systems based on wearable sensors for livestock monitoring are becoming increasingly popular. Specifically, wireless in-body sensors could yield relevant data, such as ruminal temperature. The collection of such data requires an accurate characterization of the in-to-out body wireless channel between the in-body sensor and the gateway. The aim of this study is to experimentally characterize the in-to-out-body propagation loss for cows and horses at 433, 868, and 1400 MHz. Measurements were conducted in vivo on five different fistulated cows and five horse cadavers using specialized robust in-body capsule antennas inside the animals’ abdomen. Next, the in-body antenna gain was deembedded from the wireless channel, and the in-to-out body propagation loss was obtained as the difference between measured unobstructed line-of-sight path losses and in-to-out-body path losses. The measurements showed a body propagation loss of (mean ± standard deviation) 30.8 ± 4.1 dB, 44.5 ± 4.8 dB, and 54.2 ± 4.7 dB for cows at 433, 868, and 1400 MHz, respectively. For horses, the body propagation losses were 23.2 ± 3.8 dB, 31.0 ± 4.7 dB, and 44.4 ± 3.2 dB at 433, 868, and 1400 MHz, respectively. These results are important to determine the wireless range of WBANs to optimize the network topology and estimate the associated network cost for large-scale monitoring systems. [ABSTRACT FROM AUTHOR]

A novel localization framework is presented based on ultra-wideband (UWB) channel sounding, employing a triangulation method using the geometrical properties of propagation paths, such as time delay of arrival, angle of departure, angle of arrival, and their estimated variances. In order to extract these parameters from the UWB sounding data, an extension to the high-resolution RiMAX algorithm was developed, facilitating the analysis of these frequency-dependent multipath parameters. This framework was then tested by performing indoor measurements with a vector network analyzer and virtual antenna arrays.The estimated means and variances of these geometrical parameters were utilized to generate multiple sample sets of input values for our localization framework. Next to that, we consider the existence of multiple possible target locations, which were subsequently clustered using a Kim–Parks algorithm, resulting in a more robust estimation of each target node. Measurements reveal that our newly proposed technique achieves an average accuracy of 0.26, 0.28, and 0.90 m in line-of-sight (LoS), obstructed-LoS, and non-LoS scenarios, respectively, and this with only one single beacon node. Moreover, utilizing the estimated variances of the multipath parameters proved to enhance the location estimation significantly compared to only utilizing their estimated mean values. [ABSTRACT FROM PUBLISHER]

Wireless body area networks (WBANs) provide promising applications in the healthcare monitoring of dairy cows. The characterization of the path loss (PL) between on-body nodes constitutes an important step in the deployment of a WBAN. In this paper, the PL between nodes placed on the body of a dairy cow was determined at 2.45 GHz. Finite-difference time domain simulations with two half-wavelength dipoles placed 20 mm above a cow model were performed using a 3-D electromagnetic solver. Measurements were conducted on a live cow to validate the simulation results. Excellent agreement between measurements and simulations was achieved and the obtained PL values as a function of the transmitter–receiver separation were well fitted by a lognormal PL model with a PL exponent of 3.1 and a PL at reference distance (10 cm) of 44 dB. As an application, the packet error rate (PER) and the energy efficiency of different WBAN topologies for dairy cows (i.e., single-hop, multihop, and cooperative networks) were investigated. The analysis results revealed that exploiting multihop and cooperative communication schemes decrease the PER and increase the optimal payload packet size. The analysis results revealed that exploiting multihop and cooperative communication schemes increase the optimal payload packet size and improve the energy efficiency by 30%. [ABSTRACT FROM PUBLISHER]

A comprehensive polarimetric distance-dependent model of the power delay profile (PDP) and path gain is proposed. The model includes both specular multipath components (SMCs) and dense multipath components (DMC), the latter being modeled with an exponential and power law. The parameters of the model were estimated from polarimetric measurements of a large hall radio channel under line-of-sight (LOS) conditions at 1.3 GHz with a dedicated procedure. The validity and robustness of the proposed approach are provided by the good agreement between the polarimetric data and models for the investigated transmitter–receiver distance range. Furthermore, the description of the radio channel with path loss models is discussed for cases where the DMC is included, and a two-step method to compute the path loss characteristics directly from the measured data is developed. The results of this contribution highlight the fact that a complete polarimetric description of all propagation mechanisms and related path loss models is desired to design faithful polarimetric radio channel models. [ABSTRACT FROM PUBLISHER]

An analysis of delay-Doppler characteristics in the presence of moving people is presented for short-range communication in an indoor environment. Channel-sounding measurements have been carried out at 3.6 GHz in a crowded university hall during several short and long breaks in-between courses. During three consecutive days, the measurements were repeated with different positions for the transmit and receive antennas. In this study, the behavior of the maximum Doppler shift and the Doppler spread was analyzed in the time-delay domain as a function of the occupation of the hall, the polarizations of the $2\times 2$ MIMO antennas, and their positions in the hall. The measurements reveal a clear distinction between the Doppler spread of the short and long breaks in the campaign, indicating a distinctive power distribution of their Doppler spectra. In addition, there is a significant contrast between the Doppler characteristics of the co- and cross-polarizations. Measurements at several positions reveal the importance of characterizing multipaths and show that the Doppler effect depends on the position of the antennas in the environment. In addition, this work also shows that the Doppler spectrum can be accurately modeled by a Cauchy distribution, allowing for the generation of parameters to describe Doppler characteristics. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of the polarization characteristics of specular and dense multipath components (SMC and DMC) in a large industrial hall based on frequency-domain channel sounding experiments at 1.3 GHz with 22-MHz bandwidth. Twenty-nine positions were measured under line-of-sight (LOS) and obstructed LOS (OLOS) scenarios. The RiMAX maximum-likelihood estimator is used to extract the full-polarimetric SMC and DMC from the measurement data by taking into account the polarimetric radiating patterns of the dual-polarized antennas. Cross-polar discrimination (XPD) and copolar ratio (CPR) values are presented from the measured and de-embedded channels, as well as the polarimetric delay and angular spread distributions. Strong de-embedded SMC depolarization is obtained for the horizontal polarization in OLOS scenarios. Additionally, DMC depolarization is observed to be weaker than previously reported for indoor environments but constant across LOS/OLOS, polarization, and distance. The results also show that the copolar (cross-polar) DMC power to total channel power ratio is equal to 15% (40%) for LOS and 40% (60%) for OLOS and that this ratio does not correlate significantly with transmitter–receiver distance. Finally, the validity of the room electromagnetics theory was confirmed for transmitter–receiver distances larger than 15 m with no significant difference between polarized subchannels. [ABSTRACT FROM PUBLISHER]

This paper introduces a novel formalism to improve the performance of an off-body system by deploying multiple ultra wideband (UWB) antennas, positioned strategically on the body. A methodology is presented for determining the optimal positions of UWB antennas on the body, necessary to provide a reliable multiband orthogonal frequency division multiplexing (MB-OFDM) UWB diversity antenna system operating in the Federal Communications Commission frequency band between 3.1 and 10.6 GHz. By evaluating the diversity metric, using simulation and measurement data, it is shown that the performance of such a system is stable throughout the entire investigated frequency band for both indoor and outdoor environments. There is a good agreement between the simulated and measured diversity values with a deviation of less than 9%. Therefore, the proposed technique optimizes the antennas’ positions for maximum diversity performance within a very broad frequency band, independent of the used wireless communication standard. Thus, the obtained diversity system might be used in any kind of wireless communication link within that frequency band, e.g., UWB-OFDM, UWB MB-OFDM, UWB, or even narrowband transmission. [ABSTRACT FROM PUBLISHER]

This work presents an analysis of dense multipath components (DMC) in an industrial workshop. Radio channel sounding was performed with a vector network analyzer and virtual antenna arrays. The specular and dense multipath components were estimated with the RiMAX algorithm. The DMC covariance structure of the RiMAX data model was validated. Two DMC parameters were studied: the distribution of radio channel power between specular and dense multipath, and the DMC reverberation time. The DMC power accounted for 23% to 70% of the total channel power. A significant difference between DMC powers in line-of-sight and nonline-of-sight was observed, which can be largely attributed to the power of the line-of-sight multipath component. In agreement with room electromagnetics theory, the DMC reverberation time was found to be nearly constant. Overall, DMC in the industrial workshop is more important than in office environments: it occupies a fraction of the total channel power that is 4% to 13% larger. The industrial environment absorbs on average 29% of the electromagnetic energy compared to 45%–51% for office environments in literature: this results in a larger reverberation time in the former environment. These findings are explained by the highly cluttered and metallic nature of the workshop. [ABSTRACT FROM PUBLISHER]

We present a room electromagnetics-based theory which primarily models the diffuse multipath components (DMC) power density with a simple circuit model, and afterwards includes the line-of-sight (LOS) component to predict the total exposure in a realistic environment. Given a human absorption cross section (ACS) and its location from a transmitter (Tx), the average whole-body specific absorption rate (\SARwb) can be determined by the proposed circuit model for ultra-wideband (UWB) and wireless local area network (WLAN) systems. The \SARwb in humans in a realistic office environment for both UWB and WLAN systems is investigated as part of application. The theory is simulated with the Advanced Design System (ADS) software, and excellent agreement between theoretical and simulated values are obtained in terms of relative errors (<2%). The model may be very useful for \SARwb prediction in realistic complex indoor environments. [ABSTRACT FROM PUBLISHER]

We present a flexible folded slot dipole implantable antenna operating in the Industrial, Scientific, and Medical (ISM) band (2.4–2.4835 GHz) for biomedical applications. To make the designed antenna suitable for implantation, it is embedded in biocompatible Polydimethylsiloxane (PDMS). The antenna was tested by immersing it in a phantom liquid, imitating the electrical properties of the human muscle tissue. A study of the sensitivity of the antenna performance as a function of the dielectric parameters of the environment in which it is immersed was performed. Simulations and measurements in planar and bent state demonstrate that the antenna covers the complete ISM band. In addition, Specific Absorption Rate (SAR) measurements indicate that the antenna meets the required safety regulations. [ABSTRACT FROM AUTHOR]

In this paper, an accurate method is developed to model dipole antennas In free-space or near an infinite perfectly electrical conducting plate. The magnetic field integral equation Is implemented and point-matching Is used to construct the interaction matrix. The edges of the cylinder, which can cause numerical instabilities in the simulated current distribution, are getting a special treatment by choosing a specific set of basis functions. The excitation is modeled based on the equivalence principle and leads to the application of a magnetic surface current over the gap region. The exact kernel of the integral equation is applied and all possible current components are taken into account. When the antenna Is close to a conducting plate, a strong modification of the surface current distribution is observed. It Is demonstrated that for these configurations, the Incorporation of the circumferential component of the surface current distribution is needed. At larger distances, the circumferential surface current can be neglected in the total distribution. The only approximation (or rather assumption) we made is that we impose a longitudinal directed electrical field over the boundary of the gap region. The results are verified experimentally. [ABSTRACT FROM AUTHOR]