Interest in Wireless Body Area Networks (WBANs) has increased significantly in recent years thanks to the advances in microelectronics and wireless communications. Owing to the very stringent application requirements in terms of reliability, energy efficiency, and low device complexity, the design of these networks requires the definition of new protocols with respect to those used in general purpose wireless sensor networks. This motivates the effort in research activities and in standardisation process of the last years. This survey paper aims at reporting an overview of WBAN main applications, technologies and standards, issues in WBANs design, and evolutions. Some case studies are reported, based on both real implementation and experimentation on the field, and on simulations. These results have the aim of providing useful insights for WBAN designers and of highlighting the main issues affecting the performance of these kind of networks.

A Survey on Wireless Body Area Networks: Technologies and Design Challenges

In this paper, we present the design, simulation, and measurement of a dual-band metamaterial absorber in the microwave region. Simulated and experimental results show that the absorber has two perfect absorption points near 11.15GHz and 16.01GHz. Absorptions under difierent polarizations of incident EM waves are measured with magnitude of over 97% at low-frequency peak and 99% at high-frequency peak respectively. Current distribution at the dual absorptive peaks is also given to study the physical mechanism of power loss. Moreover, it is verifled by experiment that the absorptions of this kind of metamaterial absorber remain over 90% at the low-frequency peak and 92% at the high-frequency peak with wide incident angles ranging from 0 - to 60 - for both transverse electric wave and transverse magnetic wave.

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Perfect Metamaterial Absorber with Dual Bands

A new compact planar ultrawideband (UWB) antenna designed for on-body communications is presented. The antenna is characterized in free space, on a homogeneous phantom modeling a human arm, and on a realistic high-resolution whole-body voxel model. In all configurations it demonstrates very satisfactory features for on-body propagation. The results are presented in terms of return loss, radiation pattern, efficiency, and E-field distribution. The antenna shows very good performance within the 3-11.2 GHz range, and therefore it might be used successfully for the 3.1-10.6 GHz IR-UWB systems. The simulation results for the return loss and radiation patterns are in good agreement with measurements. Finally, a time-domain analysis over the whole-body voxel model is performed for impulse radio applications, and transmission scenarios with several antennas placed on the body are analyzed and compared.

A Compact UWB Antenna for On-Body Applications

A comparison between difierent modern population based optimization methods applied to the design of scannable circular antenna arrays is presented in this paper. This design of scannable circular arrays considers the optimization of the amplitude and phase excitations across the antenna elements to operate with optimal performance in the whole azimuth plane (360 - ). Simulation results for scannable circular arrays with the amplitude and phase excitation optimized by genetic algorithms, particle swarm optimization and the difierential evolution method are provided. Furthermore, in order to set which design case could provide a better performance in terms of the side lobe level and the directivity, a comparative analysis of the performance of the optimized designs with the case of conventional progressive phase excitation is achieved. Simulation results show that

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A Comparison of Genetic Algorithms, Particle Swarm Optimization and the Differential Evolution Method for the Design of Scannable Circular Antenna Arrays

In order to protect the environment and slow down global warming trend, many governments and environmentalists are keen at promoting the use of plug-in hybrid electric vehicles (PHEVs). As a result, more and more PHEVs have been put into use. However, load peak caused by their disordered charging can be detrimental to an entire power grid. Several methods have been proposed to establish ordered PHEV charging. While focusing on single-objective load scheduling, they fail to meet the real requirements that need one to conduct multiple objective optimization. This paper formulates a multi-objective load scheduling problem to minimize two competing objectives: 1) potential serious peak-to-valley difference and 2) economic loss. When we apply existing multi-objective evolutionary algorithms (MOEAs), i.e., multi-objective particle swarm optimization (MOPSO), Nondominated Sorting Genetic Algorithm II, MOEA based on decomposition, and multi-objective differential evolutionary algorithm to solve it, because its high dimension and special conditions we find that they fail to reach the Pareto Front or converge into a relatively small area only. Therefore, we propose a weight aggregation (WA) strategy and implement a novel MOEA algorithm named WA-MOPSO by incorporating WA into MOPSO to solve the problem. Its effectiveness and efficiency to generate a Pareto front of this problem are verified and compared with those of the state-of-the-art approaches. Furthermore, WA is also combined with other MOEAs to solve the defined scheduling problem.

Optimal Load Scheduling of Plug-In Hybrid Electric Vehicles via Weight-Aggregation Multi-Objective Evolutionary Algorithms

The major deficiency of conventional ‘balanced antipodal Vivaldi antenna’ (BAVA) is its tilted beam over upper working frequencies. This study reports on a new BAVA to overcome this defect. By applying a dielectric lens in front of the antenna's aperture, beam-tilting in E-plane was improved within the ultra-wideband frequency range, as well as higher frequencies. In the new BAVA, the authors have also achieved an acceptable cross-polarisation. Measurements show that the antenna has better than 10 dB return loss within the aforesaid frequency range. The measurements successfully verify the simulation results. Group delay and fidelity factor as time domain characteristics of the proposed antenna have been studied. They have compared performance of the conventional BAVA, with achievements of the new BAVA as hereunder.

Dielectric lens balanced antipodal Vivaldi antenna with low cross-polarisation for ultra-wideband applications

A method to obtain optimum tradeoffs (Pareto front) between sidelobe level (SLL) and beamwidth (BW) in time domain for ultrawideband (UWB) antenna arrays is presented. Multiobjective particle swarm optimization (MOPSO) is used to deal with these two conflicting objectives. In the optimization process, mutual coupling effects between elements are not considered. However, the multiple solutions obtained from MOPSO enable the designer to consider the mutual coupling effect as an additional constraint. Each element of the array is an antipodal Vivaldi antenna. The optimization template is applied for three different time-domain pattern descriptors. In comparison to arrays with the same number of elements reported in literature, the Pareto fronts obtained in this study provide lower BW and SLL. A four-element sample from resultant Pareto fronts was simulated by using CST Microwave Studio software. This array shows a 13.7-17.2 dBi gain over the whole frequency band from 3-11 GHz, 7.2° BW, and -12 dB SLL for energy pattern.

Time-Domain Design of UWB Vivaldi Antenna Array Using Multiobjective Particle Swarm Optimization

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Modified Multi-Objective Particle Swarm Optimization for Electromagnetic Absorber Design

A new configuration of the dual-band and dual-polarized antenna is presented, which is fed by aperture coupling for the existing mobile communication systems working over 870-960 MHz (GSM) and 1710-2180 MHz (DCS/UMTS) frequency band. XX-Polar antenna stands for an antenna with dual-band and dual linear slant polarization. In this paper DU band stands for DCS/UMTS band. Measurement results show that the proposed antenna yields good broadside radiation characteristics including symmetric radiation patterns, low cross-polarization level ( ; 20 dB) and high isolation (>; 30 dB) at both bands. The designed antenna has an impedance bandwidth of 20.4% (790-970 MHz) for VSWR <; 1.5 in the lower band and 29.3% for VSWR <; 1.6 (1630-2190 MHz) in the upper band. The measured average gains are about 9.3-10.2 and 8.6-10 dBi in the lower and upper band, respectively. It is also promising for array antenna in various wireless systems.

High-Isolation XX-Polar Antenna

This letter proposes a simple design approach to gain stable omnidirectional radiation pattern in printed ultrawideband (UWB) antennas. Monitoring of the current distributions in different frequencies shows that a combination of standing and traveling modes exists on the antenna. By determining the dominant mode at higher and lower frequencies, the corresponding optimum size of antenna that guarantees a stable omnidirectional radiation pattern and a good return loss is obtained. Using the proposed method, two compact antennas with circular ground and miniaturized fractal ground are designed. Simulation and measurement results show a good impedance matching and an excellent omnidirectional radiation pattern for proposed antennas.

S. A. Mirtaheri

Papers

Dielectric lens balanced antipodal Vivaldi antenna with low cross-polarisation for ultra-wideband applications

Time-Domain Design of UWB Vivaldi Antenna Array Using Multiobjective Particle Swarm Optimization

Modified Multi-Objective Particle Swarm Optimization for Electromagnetic Absorber Design

High-Isolation XX-Polar Antenna

Systematic Design of UWB Monopole Antennas With Stable Omnidirectional Radiation Pattern