Showing papers by "Jianqing Wang published in 2013"

Propagation models for IEEE 802.15.6 standardization of implant communication in body area networks

Abstract: A body area network is a radio communication protocol for short-range, low-power, and highly reliable wireless communication for use on the surface, inside, or in the peripheral proximity of the human body Combined with various biomedical sensors, BANs enable realtime collection and monitoring of physiological signals Therefore, it is regarded as an important technology for the treatment and prevention of chronic diseases, and health monitoring of the elderly The IEEE 802 LAN/MAN Standards Committee approved Task Group TG156 in December 2007 As a result of more than four years of effort, in February 2012, TG156 published the first international standard for BANs, IEEE Std 802156 Throughout the development of this standard, ample collaboration between the standardization group and the research community was required In particular, understanding the radio propagation mechanisms for BANs demanded the most research effort Technical challenges were magnified for the case of implant communication because of the impossibility of conducting in-body measurements with human subjects Therefore, research in this field had to make use of intricate computer simulations This article outlines some of the research that has been done to obtain accurate propagation models supporting the standardization of implant communication in BANs Current research to enhance the channel models of IEEE Std 802156 through the use of ultra wideband signals for implantable devices along with physical measurements in animals is also presented

Dosimetry of a Reverberation Chamber for Whole-Body Exposure of Small Animals

Abstract: In order to determine the whole-body exposure level in small animals inside a reverberation chamber (RC), an ideal electromagnetic (EM) environment has often been assumed inside an RC for numerical dosimetry analyses. In an RC where a strong EM coupling between antennas and animals exists, however, such an EM environment is difficult to be realized, so that it remains unknown whether or not the RC could provide a target dosimetry. In this study, we adopt the Poggio-Miller-Chang-Harrington-Wu-Tsai formulation of the method of moments to directly determine the specific absorption rate (SAR) of a rectangular dielectric phantom placed in an RC, and we demonstrated its validity via comparing the numerical temperature rise with those obtained from experiments. We then demonstrated a nonideal EM environment inside an RC using a prolate spheroid as an exposure target. Furthermore, we performed dosimetry evaluation for multiple rat-shaped tissue-equivalent phantoms inside the RC and determined their whole-body average SARs for many orientations and arrangements of the phantoms. Finally, based on our numerical results, we offered a design rule when using an RC as a whole-body exposure system for small animals.

Design of ultra wide-band low-band implant antennas for capsule endoscope application

Abstract: This paper investigated two kinds of design of implant antennas in ultra wide-band (UWB) low-band (34-48 GHz) for capsule endoscopes First, two kinds of hemispherical antennas, one has a helical structure and the other has a loop structure, were designed The hemispherical antennas match for the shape of capsule endoscopes The reflection coefficient S11 and the directivity of the hemispherical antennas in UWB low-band were investigated in detail Next, a simplified planar design of the hemispherical loop antenna was proposed for being easy to fabricate The characteristic of the planar loop antenna in UWB low-band was investigated by both numerical simulation and experiment In addition to the S11, the path loss of the fabricated planar loop antenna was also measured in a fluid phantom simulating a human body tissue, with a planar unbalance dipole antenna as the receiving antenna The measured path loss was compared with the simulated result, and good agreement was confirmed between them

The ultra wideband capsule endoscope

Abstract: One of the most innovative applications of wireless technology in medicine is the capsule endoscope (CE). This electronic device helps to examine hard-to-reach parts of the gastrointestinal (GI) tract with significantly less discomfort for the patient than traditional endoscopic methods based on the insertion of flexible tubes. A CE has the size and shape of a pill, and after being swallowed it transmits wirelessly images of the GI tract to an external receiver worn by the patient. The images are captured with the aid of an integrated tiny camera and a light source. Through the use of sophisticated software, a video is created offline with the received images for analysis and inspection by the medical staff. In most cases, real-time video transmission is not possible. A number of commercial CE systems operating with narrowband radio interfaces are already available. Nevertheless, the quality of the CE video is generally poorer than conventional endoscopy's. The use of an ultra wideband (UWB) radio interface, which can enable high data rate transmission, would significantly enhance the video quality and reduce power consumption. The low power consumption feature could be exploited to add functional tools for purposes like biopsy or targeted drug delivery to current CE systems. Nevertheless, the high attenuation of radio signals propagating through living tissues in frequencies above 1 GHz make the use of UWB radio links for this application a major challenge. In addition, the design of an appropriate high data rate transmitter and a tiny antenna for efficient transmission over a large bandwidth are complicate tasks that require an accurate characterization of the channel. This paper presents the most important research results that we have obtained towards the implementation of a UWB-CE. Challenges and research problems in this area are outlined.

Performance evaluation on correlation detection and energy detection for ultra wideband-impulse radio communication with multi-pulse position modulation scheme in implant body area networks

Abstract: Ultra wideband-impulse radio (UWB-IR) transmission, which can provide high data rate for real-time transmission and low-power consumption in transceivers, is one of promising transmission technologies in implant body area networks (BANs) Some studies on UWB-IR propagation characteristics in implant BANs have reported that UWB-IR signals suffer from large attenuation in human body channels It is therefore necessary to clarify the actual performance of UWB-IR modulation and demodulation methods in implant BANs In this study, the authors focus on experimental evaluation of the correlation detection and energy detection for UWB-IR transmission with multi-pulse position modulation (MPPM) For this purpose, the authors develop a UWB-IR communication system with MPPM scheme, and experimentally evaluate the transmission performance of the developed systems with the two detection methods In addition to the experimental evaluation, the authors also theoretically analyse the bit-error rate (BER) performance of the correlation detection and energy detection methods by using Gaussian approximation From the experimental results, the developed system has achieved a BER of 10 -2 at the propagation loss of 75 dB with a data rate of 2 Mbps in the correlation detection This result shows the feasibility of reliable UWB-IR communication in actual implant BANs

A modified particle filter algorithm for wireless capsule endoscope location tracking

Abstract: Tracking a capsule endoscope location is one of promising application offered by implant body area networks (BANs) In this paper, we pay attention to a particle filter algorithm with received signal strength indicator (RSSI)-based localization in order to solve the capsule endoscope location tracking problem, which assumes a nonlinear transition model on the capsule endoscope location However, the original particle filter requires to calculate the particle weight according to its condition (namely, its likelihood value), while the transition model on capsule endoscope location has some model parameters which cannot be estimated by received wireless signal Therefore, for the purpose of applying the particle filter to the capsule endoscope tracking, this paper makes some modifications in the resampling step of the particle filter algorithm Our computer simulation results demonstrates that the proposed tracking methods with the modified particle filter can improve the performance as compared with not only the conventional maximum likelihood (ML) localization but also the original particle filter-based location tracking

Performance and Validation of a Broadband- Multigeneration Exposure System for Unconstrained Rats

Abstract: In view of actual electromagnetic environment of multiple-frequency exposure, we have developed a whole-body exposure system for a multigeneration bio-effect test with rats at frequencies between 800 MHz and 5.2 GHz. We first experimentally evaluated the system performances such as antenna performance, electric field distribution, and specific absorption rate (SAR) in the exposure system. Then, after an experimental validation of the finite-difference time-domain modeling of the exposure system, we employed it to make a statistical SAR analysis for anatomical rat models. We first took documentary photographs of rat activity inside the exposure system every 5 min in real time. Then, by identifying the rat positions in each photograph, we derived the frequency of rats staying in various positions in the exposure system. Using the stay frequency as a weighting factor, we derived the whole-body average SAR statistical characteristics for the multiple-frequency exposure system during the entire multigeneration experimental period. The developed system and demonstrated approach provide a high-quality means for biological effect test of radio frequency exposure in wide frequency bands.

Performance evaluation on dual-mode transceivers in wireless body area networks

Abstract: Wireless body area network (BANs) have attracted a lot of attention as a future technology of wireless networks. Wireless BANs are generally divided into two kinds of groups, i.e., on-body BANs and in-body BANs. However, the performance requirements and channel propagation characteristics of the two BANs are quite different from each other, that is, wireless signals are approximately transmitted along the human body as a surface wave in on-body BANs, on the other hand, the signals are transmitted through the human tissue in in-body BANs. As a solution for this problem, this paper develops a structure of dual-mode transceivers, which is composed of transmitters for in-body and on-body communications and a receiver for the both communications. Then, we evaluate the communication performance of the dual-mode transceivers via a computer simulation with realistic channel models, which can well represent the propagation characteristics of on-body and in-body communications. Our computer simulation results demonstrate the feasibility of the dual-mode transceiver structure in wireless BANs.

Statistical Outliers in Voxel SARs and their Effect of Whole-Body Average SARs in Pregnant Woman and Child for Far-Field Exposure

Abstract: SUMMARY The World Health Organization (WHO) recommended the necessity of electromagnetic (FM) dosimetry evaluation of pregnant women with fetus and of children as an urgent research subject in 2006, with emphasis on studies of whole-body average specific absorption rates (WBA-SARs) in various numerical models of pregnant woman and children for the purpose of determining the safety limits of WBA-SARs. The current safety limits were determined on the basis of behavior abnormalities in healthy adult animals in radio-frequency FM exposure and FM absorption characteristics at resonant frequencies, but not in experiments using pregnant and young animals. In this investigation, we calculated the voxel SARs and WBA-SARs in anatomically detailed models of pregnant woman and 3-year-old children at their resonant frequencies. The histograms and cumulative relative distributions of the voxel SARs were also derived to determine statistical outliers in the voxel SARs for pregnant woman and 3-year-old child models. We found that the mean voxel SARs agree with the WBA-SARs, and that median voxel SARs in the pregnant woman and 3-year-old child models are 47% and 55% of their means, respectively, and the peak voxel SARs are 70 times the mean in both cases. This suggests the possibility that finite-difference time-domain (FDTD)–calculated WBA-SARs may be overestimated due to the existence of statistical outliers. It was also found that although the total number ratio of voxel SARs for the outliers is 0.36% for the pregnant woman model and 0.34% for the 3-year-old child model, WBA-SARs excluding these outliers are less than those in the pregnant woman and 3-year-old child models by 6.8% and 5.7%, respectively.

Investigation of relationship between SAR and required communication performance for wireless capsule endoscope

Abstract: In this paper, we investigate local peak specific absorption rate (SAR) based on required communication performance for a wireless capsule endoscope at 400 MHz medical implant communication service (MICS) band. First, in order to calculate the bit error rate (BER) performance under this implant propagation channel and derive the required transmit power to secure a permissible BER, we perform finite-difference time-domain (FDTD) simulations for implant body area network (BAN) channel modeling with two numerical human body models. Secondly, we calculate the local peak SAR under the required transmit power when the implant transmitter moves along the digestive organs. Based on such an approach, we attempt to determine a threshold transmit power which could be used to ensure the induced SAR not exceeding the safety guideline in the human body.

Development of impulse radio HBC transceiver for vital signal monitoring of drivers

Abstract: Human body communication (HBC) technology provides a promising physical layer for wireless body area networks in healthcare, medical and entertainment applications. In this study, we developed an impulse radio (IR) type HBC transceiver for monitoring vital signals of drivers in a car. The basic structure of the transceiver was described and its communication performance were evaluated experimentally. The results show a sufficient feasibility to realize a HBC transmission at a data rate as high as 1.2 Mbps from the human chest to a fingertip.

Reduction effects of geometrical configuration on FM-band cross-talks between two parallel signal traces on vehicle-mounted printed circuit boards

Abstract: Electromagnetic disturbances in vehicle-mounted FM radios are mainly caused by conducted noise currents flowing through wiring-harnesses from printed circuit boards (PCBs). To suppress these kinds of noise currents, we previously investigated the FM-band cross-talks between two parallel signal traces on two-layer PCBs with slit ground patterns, and showed that the cross-talks cannot always be reduced by widening the width of the divided ground patterns from finite-difference time-domain (FDTD) simulations and measurements. In this paper, to examine geometrical configuration effects in reducing the FM-band cross-talks, we further performed the FDTD simulations for new-type PCBs on which two signal traces were kept in the centre of their corresponding ground patterns. The result showed that the wider the ground slit width is, the smaller the cross-talks become. To explain the difference between the above findings, we calculated the mutual inductances ‘M’ between the two signal trace circuits for the previous and new-type PCBs, which largely affect the cross-talks, and found that both Ms have the same dependence of the ground slit width as the cross-talks.

System development and performance evaluation on detection schemes for UWB-IR implant communications

Abstract: Ultra wideband-impulse radio (UWB-IR) transmission is one of promising transmission technologies in implant body area networks (BANs). Although some studies have investigated the channel model and communication architecture in implant BANs, no study quantitatively shows the feasibility of UWB-IR communication in the human body with actual developed transceivers at a high data rate. In this paper, we focus on experimental evaluation of the correlation detection (coherent detection) and the energy detection (non-coherent detection) for UWB-IR transmission with multi-pulse position modulation (MPPM). For this purpose, we develop a UWB-IR communication system with MPPM scheme, and experimentally evaluate the transmission performance of the developed systems with the two different detection schemes. In addition to the experimental evaluation, we also theoretically analyze the bit error rate (BER) performance by using Gaussian approximation. From the experimental results, the developed system has achieved a BER of 10-2 at the propagation loss of 75 dB with a data rate of 2Mbps in the correlation detection. This result shows the feasibility of reliable UWB-IR communication in actual implant BANs.