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Human Body Modelling for Wireless Body Area Network Optimization
... To ensure high-performance IoB healthcare monitoring and management services, IoB sensors should be efficiently designed and optimized for high-speed data transmission and low power consumption. Due to the limitations of the real model of the human body with its physiological characteristics, most researchers utilize traditional techniques based on phantoms to verify the IoB performance [10][11][12][13][14][15][16]. These techniques increase the uncertainty of the desired results. ...
The Internet of Body (IoB), a subset of wireless sensor networks, has emerged as a promising technology in the biomedical field. The applications of the IoB, particularly in healthcare and medical applications, have attracted significant attention in recent years. The IoB, also known as a Wireless Body Area Network (WBAN), consists of small sensors placed on the human body, which can collect physiological data and facilitate remote operations such as processing, treatment, assessment and decision-making via the Internet network. This paper presents detailed theoretical and experimental studies on the design of sensors for a 5G-based IoB healthcare monitoring network. The need for efficient and high-performance sensors, in the healthcare industry for enabling continuous monitoring of patient’s health in real-time, is highlighted along this work. In this paper, we propose a novel approach for designing and analyzing the performance of IoB antenna sensors, specifically focusing on channel modeling and power-consumption between wearable wireless sensors. The behavior of the sensors on the human body is studied both theoretically and experimentally for two optimal locations: on the human body waist and on human arm-hand. The results are compared to assess the accuracy of the theoretical model. Despite the complexity of the physiological behavior of the human body, our findings show a good agreement between the theoretical and experimental results. This work provides valuable insights into the design and optimization of IoB/WBANs for real-world medical applications.
... In this paper, we propose a convolutional neural network (CNN) for modeling the power density map in a very complex domain as the human body is. Since full-wave simulations are computationally expensive [5], the proposed method could be a promising solution to this problem. ...
Determining the amount of electromagnetic wave energy absorbed by the human body is an important issue in the analysis of wireless systems. Typically, numerical methods based on Maxwell's equations and numerical models of the body are used for this purpose. This approach is time-consuming, especially in the case of high frequencies, for which a fine discretization of the model should be used. In this paper, the surrogate model of electromagnetic wave absorption in human body, utilizing Deep-Learning, is proposed. In particular, a family of data from finite-difference time-domain analyses makes it possible to train a Convolutional Neural Network (CNN), in view of recovering the average and maximum power density in the cross-section region of the human head at the frequency of 3.5 GHz. The developed method allows for quick determination of the average and maximum power density for the area of the entire head and eyeball areas. The results obtained in this way are similar to those obtained by the method based on Maxwell's equations.
... Numerical models of the human body are widely used to design wireless systems that operate in this complex environment [20]. Depending on the exact application of such models, they differ in shape and internal structure [21]. They can be made of one material (homogeneous models) or from many materials of different electric properties (heterogeneous models). ...
Wireless capsule endoscopes take and send photos of the human digestive tract, which are used for medical diagnosis. The capsule’s location enables exact identification of the regions with lesions. This can be carried out by analyzing the parameters of the
electromagnetic wave received from the capsule. Because the human body is a complex heterogeneous environment that impacts the propagation of wireless signals, determining the distance between the transmitter and the receiver based on the received power level is challenging. An enhanced approach of identifying the location of endoscope capsules using a wireless signal phase detection algorithm is presented in this paper.
For each capsule position, this technique uses adaptive estimation of human body model permittivity. This approach was tested using computer simulations in Remcom XFdtd software using a numerical, heterogeneous human body model, as well as measurements with physical phantom. The type of transmitting antenna employed in the capsule also has a significant impact on the suggested localization method’s accuracy. As a result, the helical antenna, which is smaller than the dipole, was chosen as the signal’s source. For both the numerical and physical phantom studies, the proposed technique with adaptive body model enhances localization accuracy by roughly 30%.
This letter proposes a novel electromagnetic (EM) optimization approach using adjoint-sensitivity-based multifeature surrogate for microwave filter design. The proposed technique aims to solve the EM optimization problem, in which the starting point is far from the design specifications. We propose to add feature sensitivities in multifeature surrogate modeling to achieve a more accurate surrogate compared with the existing methods without feature sensitivities. We also propose a new design objective function in feature space to further improve the efficiency of multifeature-assisted optimization. Two microwave filter examples are used to demonstrate the proposed technique.
Thanks to their arising abilities to influence the human lifestyle, along with reducing the healthcare systems’ cost, wireless body area networks (WBANs) still form a strongly growing research field. Recent advances focus on the opportunities of coexistence and communication between a group of WBANs, that will forward the sensing data, using persons as network relays, until reaching a remote analysis server or cloud servers via the Internet, forming thus a body-to-body network (BBN). Such new-style networks support a range of innovative and promising applications, including ubiquitous healthcare (U-health), interactive games, and military, to cite a few. In this paper, we first present the evolution of the single WBAN concept to the cooperative network of multiple WBANs, giving rise to the BBN concept. A synopsis of the WBAN and BBN respective standards and applications is given, and the emerging BBN challenges are highlighted. Then, we present and discuss the existing WBAN proposals, especially the candidate WBAN protocols that could be adapted and used in BBNs, focusing on four intrinsically related axes of great importance for BBN design: energy efficiency, mobility prediction, quality of service (QoS) and security. Further BBN open issues are also investigated, namely, the wireless propagation between humans carrying wearable devices, the interference, storage and privacy issues as well as the heterogeneity of BBN devices and traffic.
The purpose of this research was to improve the performance of a wireless body area sensor network, operating on a person in the seated and standing positions. Optimization-focused on both the on-body transmission channel and off-body link performance. The system consists of three nodes. One node (on the user's head) is fixed, while the positions of the other two (one on the user's trunk and the other on one leg) with respect to the body (local coordinates) are design variables. The objective function used in the design process is characterized by two components: the first controls the wireless channel for on-body data transmission between the three sensor nodes, while the second controls the off-body transmission between the nodes and a remote transceiver. The optimal design procedure exploits a low-cost Estra, which is an evolutionary strategy optimization algorithm linked with Remcom XFdtd, a full-wave Finite-Difference Time-Domain (FDTD) electromagnetic field analysis package. The Pareto-like approach applied in this study searches for a non-dominated solution that gives the best compromise between on-body and off-body performance.
In this paper the problem of optimization design of a microwave wearable antenna is investigated. Reference is made to a specific antenna design that is a wideband Vee antenna the geometry of which is characterized by 6 parameters. These parameters were automatically adjusted with an evolution strategy based algorithm EStra to obtain the impedance matching of the antenna located in the proximity of the human body. The antenna was designed to operate in the ISM (industrial, scientific, medical) band which covers the frequency range of 2.4 GHz up to 2.5 GHz. The optimization procedure used the finite-difference time-domain method based full-wave simulator with a simplified human body model. In the optimization procedure small movements of antenna towards or away of the human body that are likely to happen during real use were considered. The stability of the antenna parameters irrespective of the movements of the user’s body is an important factor in wearable antenna design. The optimization procedure allowed obtaining good impedance matching for a given range of antenna distances with respect to the human body.
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.
The paper presents the exploitation of an evolutionary algorithm (EStra) for identifying the parameters of a simplified human body model. A simplified model is well suited for computationally expensive optimization of a wearable antenna located in close proximity to the human body. An automated procedure based on evolutionary computing and Finite Difference Time Domain (FDTD) is proposed to identify the parameters of a simplified human body model. The model with identified (optimized) parameter values is compared to a heterogeneous anthropomorphic human-body model by the analysis of impedance matching of the same dipole antenna located on both phantoms, i.e. the anthropomorphic one and the simplified one. Simplified Human Body Model Design and optimization of radio communication systems that operate in close proximity to the human body, require the use of computer-aided simulations and measurements in a controlled environment. Commercially available computer models of the human body are widely used for electromagnetic simulation in computer codes based on finite difference time domain (FDTD) or finite element (FEM) method. Human body models are used for a number of purposes [1-4]. The most common application is electromagnetic dosimetry which aims at estimating the amount of energy of electromagnetic wave that is absorbed by the human body (calculation of Specific Absorption Rate). A heterogeneous phantom is capable of presenting the differences of absorbed energy density among different organs and tissues which can be used also in medical applications for microwave hyperthermia or microwave ablation. Another application of human body models is simulation of body-worn antenna performance. It covers the simulation of the antenna radiation pattern and input impedance that are both strongly influenced by the presence of the human body. For this application, anthropomorphic and heterogeneous models could be computationally expensive and moreover they do not have a direct equivalent in the form of a physical phantom for experimental investigation, which means that the results of simulations are difficult to be verified. To overcome the limitations of heterogeneous anthropomorphic models, two simplified models are investigated in this paper. Those models significantly simplify human body geometry and morphology and thus they are dedicated to be used in particular applications such as analysis of antenna radiation patterns or analysis of antenna impedance matching. This paper presents a simplified numerical model that imitates the electromagnetic properties of the human body, for the purpose of computer simulations of wearable antennas impedance mismatch resulting from the proximity of human body. In contrast to the heterogeneous models, it gives a less accurate representation of the human body, but it is easy to be implemented and simulated in computer
The paper presents a study on the application of an algorithm of evolutionary computing for the optimization of the placement of an antenna for body worn wireless sensors. It is assumed that sensors exchange data over a radio link operating in the 2.4 GHz band and they are situated on the head and the chest of the wearer. The goal of the optimization process is the minimization of signal attenuation between antenna ports which can be achieved by changing their location in the defined regions. The optimization procedure, which is fully automated, is based on a cost-effective evolution strategy for the error function minimization, coupled with a Finite Difference Time Domain simulator using a simplified human body model for the electromagnetic field analysis. Wireless Sensor Network Simulation Scenario Wireless sensor networks have a great number of applications, e.g. the medical ones, that require the placement of sensors in the proximity of the human body. Wireless sensors provide a very convenient solution for gathering medical data (temperature, heart rate) because they are unobtrusive and do not limit the comfort of patient. This can be achieved by the exploitation of miniature sensing nodes with very small batteries that reduce the available transmit power to the range of milliwatts. Another important factor which has to be considered by the designer is the attenuation of radio waves due to the presence of the human body which can change in a wide range depending on the position of the transmitter and the receiver as well as the frequency band. This in turn has a significant influence of the power budget of the radio nodes. To improve the design of the wireless sensor network that operates in the proximity of the human body the optimization process of node location can be attempted. The aim of optimization can be to maximize the coupling between the transmitter and the receiver antenna ports which will result with extended lifetime of battery supplied wireless nodes. To investigate the possibilities of this methodology a numerical experiment for a simple scenario was proposed. The subject of further investigation is a two node network that consist of a transmitter located close to the ear and a receiver located on the chest of the wearer. This idea results from the consideration of a practical case of a wireless system involving wireless pulsoximeter located on the human head with the sensor placed on the earlobe. The data transmitted from the pulsoximeter is then received and retransmitted to the base station by the wireless sensor located on the chest. The simulation scenario assumes that the sensor network transmits measurement data in the ISM 2.4 GHz frequency band with dipole antennas which is shown in Fig. 2A. The antenna arm length was equal to a=26.5mm, and antenna radius was b=0.5mm. Dipole antennas were adopted in this scenario for simplicity, while in target solutions some other antenna types could be more appropriate. The
This paper presents a study into radiation pattern measurements of an electrically small dielectric resonator antenna (DRA) operating between 2.4 and 2.5 GHz in the industrial, scientific and medical (ISM) radio band for body-centric wireless communication applications. To eliminate the distortion of the radiation pattern associated with the unwanted radiation from a metallic coaxial cable feeding the antenna we have replaced it with a fibre optic feed and an electro-optical (EO) transducer. The optical signal is then converted back to RF using an Opto-Electric Field Sensor (OEFS) system. To ensure traceable measurements of the radiation pattern performance of the wearable antenna a generic head and torso solid anthropomorphic phantom model has been employed. Furthermore, to illustrate the benefits of the method, numerical simulations of the co-polar and cross-polar H-plane radiation patterns at 2.4, 2.45, and 2.5 GHz are compared with the measured results obtained using: (i) an optical fibre; and (ii) a metallic coaxial cable.
In the paper the research on simplified numerical human body model for analysis of wireless systems operating In the proximity of posed human body is presented. The proposed simplified human body model is build with PVC pipes filled with tissue stimulant liquid. Due to its simplicity, it can be easily modified to model a sitting person. Comparable studies were made with NMR Hershey numerical heterogeneous body model that is available in Remcom XFdtd computer program. This was modified with Varipose program to model sitting person. Simplified model was compared with reference model for simulation scenarios typical for wireless body area networks. (Simplified human body model for analysis of wireless systems operating In the proximity of posed human body). Słowa kluczowe: modele ciała człowieka, FDTD, systemy bezprzewodowe, sieci BAN
Slotted PIFA on the textile substrate suitable for body-centric applications in the UHF band is proposed. The influence of slot in the ground plane on the antenna parameters is theoretically investigated using simplified model of human body.
A rigorous full-wave solution, via the Finite-Difference-Time-Domain (FDTD) method, is performed in an attempt to obtain realistic communication channel models for on-body wireless transmission in Body-Area-Networks (BANs), which are local data networks using the human body as a propagation medium. The problem of modeling the coupling between body mounted antennas is often not amenable to attack by hybrid techniques owing to the complex nature of the human body. For instance, the time-domain Green's function approach becomes more involved when the antennas are not conformal. Furthermore, the human body is irregular in shape and has dispersion properties that are unique. One consequence of this is that we must resort to modeling the antenna network mounted on the body in its entirety, and the number of degrees of freedom (DoFs) can be on the order of billions. Even so, this type of problem can still be modeled by employing a parallel version of the FDTD algorithm running on a cluster. Lastly, we note that the results of rigorous simulation of BANs can serve as benchmarks for comparison with the abundance of measurement data.
We propose to use the advantages of the multi-level dual-grid finite-difference time-domain (DG-FDTD) method to determine, in a short computation time, the transmission between an antenna implanted in a simplified homogeneous body model and a half-wavelength dipole (at 402 MHz) located in free space. The transmission coefficient is determined for four different positions of the body.
This paper deals with the shape design of the excitation unit of a magnetic induction tomography (MIT) system by means of a procedure of multiobjective design. As a result of the proposed method, a set of optimal geometries of the basic excitation structure was found.
Purpose
The purpose of this study is to develop a method to reduce the computation time necessary for the automated optimal design of dual-band wearable antennas. In particular, the authors investigated if this can be achieved by the use of a hierarchical optimization paradigm combined with a simplified human body model. The geometry of the antenna under consideration is described via eight geometrical parameters which are automatically adjusted with the use of an evolutionary algorithm to improve the impedance matching of an antenna located in the proximity of a human body. Specifically, the antennas were designed to operate in the ISM band which covers two frequency ranges: 2.4-2.5 GHz and 5.7-5.9 GHz.
Design/methodology/approach
During the studies on the automated design of wearable antennas using evolutionary computing, the authors observed that not all design parameters exhibit equal influence on the objective function. Therefore, it was hypothesized that to reduce the computation effort, the design parameters can be activated sequentially based on their influence. Accordingly, the authors’ computer code has been modified to include this feature.
Findings
The authors’ novel hierarchical multi-parameter optimization method was able to converge to a better solution within a shorter time compared to an equivalent method not exploiting automatic activation of an increasing number of design parameters. Considering a significant computational cost involved in the calculation of the objective function, this exhibits a convincing advantage of their hierarchical approach, at least for the considered class of antennas.
Research limitations/implications
The described method has been developed for the design of single- or dual-band wearable antennas. Its application to other classes of antennas and antenna environments may require some adjustments of the objective functions or parameter values of the evolutionary algorithm. It follows from the well-recognized fact that all optimization methods are to some extent application-specific.
Practical implications
Computation load involved in the automated design and optimization can be significantly reduced compared to the non-hierarchical approach with a heterogeneous human body model.
Originality/value
To the best of the authors’ knowledge, the described application of hierarchical paradigm to the optimization of wearable antennas is fully original, as well as is its combination with simplified body models.
The paper presents the exploitation of a lowest-order algorithm of evolutionary computing (EStra) for identifying the parameters of a simplified human body model (phantom). A simplified model is well suited in view of the computationally-expensive field simulation of wearable antennas located in a close proximity to the human body. In the paper, an automated procedure based on evolutionary computing and Finite Difference Time Domain (FDTD) computational electrodynamics method is proposed to identify the parameters of the simplified model. Subsequently, after identifying the parameter values, the simplified model is compared to a heterogeneous anthropomorphic human-body model. The comparison is based on the analysis of impedance matching of the same dipole antenna located on both the anthropomorphic and simplified phantoms.
In the paper the analysis of the influence of textile antenna location on its radiation pattern is presented. The analysis is based on a textile Vee type antenna proposed by the author that operates in 2.4 GHz ISM band. It was made with textile base material and conducting fibers that were embroidered to form the radiator. The antenna radiation pattern for on-body location is firstly examined with computer simulations in XFdtd program. The computer simulation results are then verified with measurements. Performance of the textile antenna is compared with a standard dipole antenna that is easily available for 2.4 GHz band.
In the paper simplified human body phantoms which can be used for modeling of wireless body area networks are proposed and investigated in 2.4 GHz band. The models approximate the human body with PCV pipes filled with tap water. Due to their simplicity, proposed physical models can be easily reproduced in any laboratory at low cost. These models also have easy to prepare numerical versions. It is shown that the simplified model can be successfully used in numerical simulations of wireless body area networks as well as in measurements. In the case of path-loss simulation between antennas located on the opposite sides of the body (on-body scenario) a good agreement between the simplified and the reference model is shown. The average values obtained for 2400MHz - 2500MHz ISM band differ by ca. 3 dB, which is satisfactory for most engineering applications. Also the measurements of the path-loss for the line-of-sight transmission obstructed by the human body were conducted. The results obtained with the simplified model and the human subject show that the simplified model can be used also in other measurement scenarios than on-body. The signal attenuation values (averaged over 360 deg. of body rotation) measured with the 6 cylinder model and the human subject differ by ca. 2 dB.
Purpose
The paper aims to compare properties of simplified physical and corresponding numerical human body models (phantoms) and verify their applicability to path loss modelling in narrowband and ultra-wideband on-body Wireless Body Area Networks. One of the models has been proposed by the authors.
Design/methodology/approach
Two simplified numerical and two physical phantoms for Body Area Network on-body channel computer simulation and field measurement results are presented and compared.
Findings
Computer simulations and measurements which were carried out for the proposed simplified 6-cylinder model with various antenna locations lead to the general conclusion that the proposed phantom can be successfully used for experimental investigation and testing of on-body WBANs both in ISM and UWB IEEE 802.15.6 frequency bands.
Research limitations/implications
Usage of the proposed phantoms for the simulation/measurement of the Specific Absorption Rate and for off-body channels are not within the scope of this paper.
Practical implications
The proposed simplified phantom can be easily made with a low cost in other laboratories and be used both for research and development of WBAN technologies. The model is most suitable for wearable antenna radiation pattern simulation and measurement.
Originality/value
A new 6-cylinder phantom has been proposed. The proposed simplified phantom can be easily made with a low cost in other laboratories and be used both for research and development of WBAN technologies.
The work presented is an assay done on the effects of wearable antenna when placed in proximity to the human body. Cloth fabric is used as a substrate to design a planar antenna. Measurement results of the fabricated patch at free space and close to the human body are also presented here. The S11 of the designed antenna when placed close to the body tissue is almost -30 dB and the gain is close to 4 dB. A rectangular three layered human body model is used to evaluate the extent of the effect that the human body has on the parameters that define an antenna like its gain, directivity, etc.
The paper presents a simplified human body model which can be used for radio channel investigation in Body Area Networks (BAN). This simplified model can be applied to computer simulation in a wide range of frequencies that are required for the analysis of the Cognitive Radio systems. It can be also easily fabricated and used as a phantom in measurements of cognitive radio channel parameters. The proposed model was compared with a heterogeneous human body model. The results of computer simulation, which were obtained with the finite difference time domain method, are presented.
This paper proposed the skeleton model to generate human body models for predicting dynamic BAN channels by considering the simplified body geometry in analytical study. The numerical human body model was exported into skeleton in bvh (bio-vision hierarchy) file format. The cylinder body model is constructed by shaping the necessary bones of skeleton by cylinder. The feasibility of model is assessed by FDTD simulation. The results show reasonable agreement between channels calculated from the complex and simplified body models. By using skeleton, the motion data can be transferred into a small size file without losing necessary information for channel prediction.
This paper presents fundamental investigation of the validity of the homogeneous tissue-equivalent phantom which is simulated human tissue structures simply and is used in general experiment for evaluations of interaction between the human body and the antenna characteristics. In this paper, the dependence of antenna characteristics on structure of analytical model was investigated. Therefore the half wavelength dipole antenna and the loop antenna were arranged near a homogeneous model and a layer structural model, and the difference of antenna characteristics by structure of model was investigated. As a result, it was confirmed that the human tissue structure had a significant effect on the antenna characteristics when the distance between the antenna and the phantom is less than 0.1λ. In contrast, in case that the distance is more than 0.3λ, the validity of the homogeneous phantom was confirmed.
To determine the effective performance of handheld cellular radio antenna, it is essential to evaluate the electromagnetic (EM) interaction between the antenna and the human body. EM evaluation using the real human bodies has drawbacks such as poor repeatability and traceability. This is because the different ways of holding the terminal give a variety of geometric relationship between the terminal and the human head and hand. To develop antennas that are less affected by the human body, the mechanisms for the variations in the characteristics with respect to the antenna structure, caused by absorption in each region of the human body, must be considered. However, measurements made with the respective parts of real human bodies are difficult. Thus, human phantoms are widely used in the various fields of antenna engineering to solve these problems. In realizing human phantoms for the purpose of antenna design, there are two points that have to be considered; (1) What kind of antenna to be estimated? (2) What kind of characteristic to be measured? This paper presents recent status and some technological issues for the development of human phantoms used for antenna designs from the above-mentioned two perspectives. Furthermore, as a new trend of phantom applications towards future wireless radios, MIMO over-the-air testing (MIMO-OTA) using a phantom and an arm-waving dynamic phantom for the assessment of body area network (BAN) systems are briefly introduced.
Some decades have passed by, since the topic of numerical optimisation has rushed into engineering, mainly boosted by the increasing availability of computational power. In turn, computational electromagnetism has so advanced, since the advent of digital computers and thanks to the development of numerical methods, that in more recent years it has been possible to integrate the analysis of electromagnetic field with optimisation techniques, so moving from computer-aided design (CAD) to automated optimal design (AOD) of systems and devices. Nowadays, in fact, the association of low-price and high-speed computers with numerical libraries makes it possible to identify solutions to inverse problems of various kind and complexity, so offering scientists and engineers the possibility of implementing AOD.
Recently, much research has been done on the interactions between the human body and electromagnetic (EM) waves radiated from antennas for mobile terminals. The "interactions" are two-way: the influence of the human body on the performance of a mobile terminal; the influence of EM waves on the human body. Such interactions are estimated by numerical simulation and/or experimental evaluation. In experimental investigations, tissue-equivalent liquid or solid phantoms are usually used for SAR (specific absorption rate) evaluation. Solid phantoms for such evaluations require various characteristics: 1) known physical characteristics; 2) easily obtained materials requiring no special equipment for fabrication; 3) electric constants with long term stability; 4) electric constants with wide frequency band; 5) low cost. The paper introduces examples of three types of "new" solid phantoms for evaluation of the interactions in various situations. First, we introduce a phantom which can realize the electric constants of the human head for 3-6 GHz. Next, a real-shaped upper-half body phantom is shown at the 2.6 GHz band. Finally, an abdomen phantom for a pregnant women is introduced at 150 MHz.