Miniaturized wireless sensors are designed to run on limited power resources, requiring minimization of transmit power and lowering of the fade margin in the link budget. One factor that has an important impact on wireless sensor network design is path loss between the transmitter and the receiver. This paper presents an analysis of the influence of human bodies on path loss in the 2.4 GHz band, which is commonly used for wireless sensor networks. The effect of body shadowing was first analyzed in full wave computer simulations using the finite-difference time-domain method. Due to the high numerical burden, the simulations were limited to only a small region around the human body. To analyze the performance of networks in larger indoor environments, a human body model is proposed that can be used for simulations with a ray-based computer program. The proposed model of human body is the main contribution of this paper. It was used to analyze the body shadowing effect in a typical indoor environment. The results were found to be in good agreement with measurements.

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.

Purpose: – The purpose of this paper is to compare the properties of simplified physical and corresponding numerical human body models (phantoms) and verify their applicability to path loss modeling in narrowband and ultra-wideband on-body wireless body area networks (WBANs). 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 six-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. Social implications: – Presented results facilitate applications of WBANs in medicine and health monitoring. Originality/value: – A new six-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.

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.

This paper describes a new design and an optimization framework for a four-band antenna to be used in wireless sensor networks. The antenna is designed to operate effectively in two open frequency bands (ISM—Industrial, Scientific, Medical), 2.4 GHz and 5.8 GHz, as well as in two bands allocated for the fifth-generation (5G) cellular networks, 0.7 GHz and 3.5 GHz. Our initial design was developed using the trial and error approach, modifying a circular disc monopole antenna widely used in ultra wideband (UWB) systems. This initial design covered the three upper bands, but impedance matching within the 700 MHz band was unsatisfactory. The antenna performance was then improved significantly using an optimization algorithm that applies a bi-objective fully-Paretian approach to its nine-parameter geometry. The optimization criteria were impedance matching and radiation efficiency. The final design exhibits good impedance matching in all four desired bands with the Voltage Standing Wave Ratio (VSWR) value below 2 and radiation efficiency of 88%. The simulated antenna performance was verified experimentally.

The paper discusses the results of research concerning the formation of electroconductive transmission lines on textile substrates using the magnetron sputtering technique. The transmission lines developed can potentially be applied in clothing for emergency and security services to affect electrical connections between electronic elements incorporated in the garments. The time of metallic layer deposition and the type of substrate used was optimised in the study. The surface resistivity, resistance to bending and abrasion of the transmission lines obtained were tested. The tests demonstrated that it is possible to obtain electroconductive copper layers with a surface resistivity approximating 0.2 Ω by direct deposition on spun-bonded type polypropylene nonwoven.