Showing papers by "Jianqing Wang published in 2012"

Channel Modeling and Performance Analysis of Diversity Reception for Implant UWB Wireless Link

Abstract: SUMMARY This paper aims at channel modeling and bit error rate (BER) performance improvement with diversity reception for in-body to on-body ultra wideband (UWB) communication for capsule endoscope application. The channel characteristics are firstly extracted from 3.4 to 4.8 GHz by using finite difference time domain (FDTD) simulations incorporated with an anatomical human body model, and then a two-path impulse response channel model is proposed. Based on the two-path channel model, a spatial diversity reception technique is applied to improve the communication performance. Since the received signal power at each receiver location follows a lognormal distribution after summing the two path components, we investigate two methods to approximate the lognormal sum distribution in the combined diversity channel. As a result, the method matching a short Gauss-Hermite approximation of the moment generating function (MGF) of the lognormal sum with that of a lognormal distribution exhibits high accuracy and flexibility. With the derived probability density function (PDF) for the combined diversity signals, the average BER performances for impulse-radio (IR) UWB with non-coherent detection are investigated to clarify the diversity effect by both theoretical analysis and computer simulation. The results realize an improvement around 10 dB on Eb/No at BER of 10−3 for two-branch diversity reception.

Development of human body communication transceiver based on impulse radio scheme

Abstract: IEEE 802156 standard has defined the human body communication (HBC) as one of physical layers for wireless body area networks in healthcare, medical and entertainment applications In this study, we developed an impulse radio (IR) type transceiver for HBC application The basic structure was described and its communication performance were evaluated The results show a sufficient feasibility to realize a HBC transmission at a data rate as high as 12 Mbps along the human body surface

Performance Evaluation on RSSI-Based Localization for Capsule Endoscopy Systems with 400MHz MICS Band Signals

Abstract: SUMMARY One of promising application offered by implant body area networks (BANs) is a capsule endoscope localization system. To begin with, this paper performs finite-difference time-domain (FDTD) simulations on implant BAN propagation with a numerical human model, and investigates the propagation characteristics of implant BAN signals at 400 MHz medical implant communication service (MICS) band. Then, the paper presents a capsule endoscope localization system which utilizes only received signal strength indicator (RSSI) and two estimation methods, such as a maximum likelihood (ML) estimation method and a least squares (LS) method. Furthermore, we evaluate the two localization methods by two computer simulation scenarios. Our computer simulation results demonstrate that the ML localization can improve the location estimation accuracy as compared with the LS localization, that is, our performance comparison reveals that a careful consideration the propagation characteristics of implant BANs signals is efficient in terms of estimation performance improvement in capsule endoscope localization.

Measurement and validation of GHz-band whole-body average SAR in a human volunteer using reverberation chamber

Abstract: The World Health Organization?s (WHO) recommendation on the need for further research for radio-frequency dosimetry has promoted studies on the whole-body average-specific absorption rate (WBA-SAR) in various kinds of anatomical-based numerical models. For experimental validation of GHz-band WBA-SARs in a real human, however, there have not so far been any published papers, despite the fact that, in 1982, Hill measured WBA-SARs at frequencies less than 40?MHz in human volunteers using a TEM-cell exposure system. In this study, we provide a measurement technique with a reverberation chamber for validating numerical dosimetry results on GHz-band WBA-SARs in living humans. We measured WBA-SARs at 1, 1.5 and 2?GHz for a 22?year old male volunteer, with a height of 173?cm and a weight of 73?kg, in the reverberation chamber, and compared the results with the finite-difference time-domain (FDTD) simulation. The reverberation chamber was excited by using a signal generator through an amplifier with an output power of 30?40 mW, which produced inside the chamber with the volunteer an average electric field strength of 5?V m?1 equivalent to an average power spectral density of 6.6 ?W cm?2. The WBA-SARs were obtained from the measured S11 and S21 together with the power density. On the other hand, the WBA-SARs have been calculated using the FDTD method for an adult male model with almost the same physique as that of the volunteer exposed to the electromagnetic field in the reverberation chamber. From the comparison between the measured and the calculated WBA-SARs, we could confirm that the measured GHz-band WBA-SARs approximately agree with the FDTD calculated results.

Impact of propagation characteristics on RSSI-based localization for 400 MHz MICS band implant body area networks

Abstract: One of promising application offered by implant body area networks (BANs) is a capsule endoscope localization system To begin with, this paper performs finite-difference time-domain (FDTD) simulations on implant BAN propagation with a numerical human model, and investigates the propagation characteristics of implant BAN signals at 400 MHz medical implant communication service (MICS) band Then, the paper presents a capsule endoscope localization system which utilizes only received signal strength indicator (RSSI) and two localization methods, such as a maximum likelihood (ML) estimation method and a least squares (LS) method Our simulation results demonstrate that careful consideration of the propagation characteristics of implant BANs signals is efficient in terms of estimation performance improvement in capsule endoscope localization

Impact of Spatial Diversity Reception on SAR Reduction in Implant Body Area Networks

Abstract: Wireless capsule endoscopy (WCE) is now one of most important applications in implant body area networks (BANs). WCE requires high throughput performance due to its real-time data transmission, whereas the communication performance depends much on the transmit power, which is strictly regulated in order to satisfy a safety guideline in terms of specific absorption rate (SAR). Spatial diversity reception is well known to improve the wireless performance without any temporal and spectral resource expansion. Additionally, applying spatial diversity reception to WCE systems can be expected to not only improve the wireless communication performance but also to reduce SAR. Therefore, this paper investigates the impact of spatial diversity reception on SAR levels for the 400 MHz medical implant communication service (MICS) band. To begin with, based on finite-difference time-domain (FDTD) simulations for implant BAN propagation with a numerical human body model, we first calculate the BER performance and derive the required transmit power to secure a permissible BER. Then, this paper calculates the local peak SAR under the required transmit power when the implant transmitter moves through the digestive organs. Finally, our simulation results demonstrate that applying spatial diversity reception can significantly reduce SAR in implant BANs. key words: SAR, Implant BANs, WCE, Spatial diversity reception

Diversity performance of UWB low band communication over in-body to on-body propagation channel

Abstract: Ultra wideband (UWB) technology in low band is promising for implant body area network. In this paper, the performance improvement of an in-body to on-body UWB communication, which corresponds to a capsule endoscope application, is investigated. We firstly analyzed the in-body to on-body propagation characteristics and proposed a two-path impulse response channel model based on finite difference time domain numerical method (FDTD) incorporated with an anatomical human model. In view of the extracted statistical characteristics of the proposed two-path model, we then employed a spatial diversity reception technique to improve the communication performance effectively. The average bit error performance was finally investigated to clarify the diversity effect with theoretical analysis and computer simulation.

Statistical determination of whole-body average SARs in a 2 GHz whole-body exposure system for unrestrained pregnant and newborn rats.

Abstract: A 2 GHz whole-body exposure to rats over a multigeneration has been conducted as part of bio-effect research in Japan. In this study, the rats moved freely in the cage inside the exposure system. From observation of the activity of rats in the cage, we found that the rats do not stay in each position with uniform possibility. In order to determine the specific absorption rate (SAR) during the entire exposure period with high accuracy, we present a new approach to statistically determine the SAR level in an exposure system. First, we divided the rat cage in the exposure system into several small areas, and derived the fraction of time the rats spent in each small area based on the classification of the documentary photos of rat activity. Then, using the fraction of time spent in each small area as a weighting factor, we calculated the statistical characteristics of the whole-body average SAR for pregnant rats and young rats during the entire exposure period. As a result, this approach gave the statistical distribution as well as the corresponding mean value, median value and mode value for the whole-body SAR so that we can reasonably clarify the relationship between the exposure level and possible biological effect.

SAR evaluation based on required BER performance for 400 MHz implant BANs

Abstract: Implant body area networks (BANs) have so far drawn considerable attention in biomedical applications. Although implant BANs require high throughput performance of wireless communication due to real-time data transmission, the transmit power is strictly regulated in order to satisfy a safety guideline in terms of specific absorption rate (SAR). In this paper, we evaluate the local peak SAR based on required bit error rate (BER) performance for implant BANs at 400 MHz medical implant communication service (MICS) band. To begin with, we first perform finite-difference time-domain (FDTD) simulations for implant BAN propagation with a numerical human body model, and derive the propagation characteristic of implant BAN signals. Then, we calculate the BER performance under this implant propagation channel and derive the required transmit power to secure a permissible BER. Finally, 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.

Effect of energy detection duration on UWB-IR transmission performance in wireless body area networks

Abstract: One of promising transmission technologies in wireless body area networks (BANs) is ultra wideband-impulse radio (UWB-IR) transmission, which can provide high data rate for real-time transmission, and extremely low power consumption for increasing device longevity. Moreover, energy detection scheme in UWB-IR transmission is advantageous in terms of simple implementation. On the other hand, UWB-IR signals suffer from large attenuation in wireless BANs, so it is important to secure high quality of UWB-IR transmission performance. In this paper, we pay attention to optimization for energy detection duration of the UWR-IR transmission to solve this problem. For this purpose, in addition to an experiment and a computer simulation, we derive the bit error rate (BER) performance by a theoretical analysis with Gaussian approximation. From the investigations, we have come to a conclusion that nevertheless several conditions are required, the theoretical analysis with Gaussian approximation can work well, that is, we achieve good agreements between the results by the experiment, the computer simulation and the theory. Furthermore, the UWB-IR transmission performance can be improved by using an optimal energy detection duration.

Approaching direction detection of human arm using human body communication technology

Abstract: Human body can be considered as a communication channel in which the electric field propagates around the body as an approximated surface wave, which is known as human body communication (HBC). HBC is superior to other wireless communications from the point of view of electromagnetic compatibility. Since the human body acts as a conductor below a few tens of MHz, one can detect the existence of human body by measuring the corresponding electric filed variation in close proximity of the human body. In this study, we made an effort to detect the approaching direction of human arm based on the HBC principle under the assumption of application to a user-machine interface. We also conducted an experimental validation for our simulation result, and attempted to provide an appropriate explanation of this detection system with an equivalent circuit model.

Split width effect of ground patterns on FM-band cross-talks between two parallel signal traces of printed circuit boards

Abstract: Electromagnetic disturbances in vehicle-mounted radios are mainly caused by conducted noise currents flowing through wiring-harnesses from vehicle-mounted printed circuit boards (PCBs) with common slitted ground patterns. To investigate suppression of these kinds of noise currents, previous measurements from simple two-layer PCBs with two parallel signal traces with slitted and non-slitted ground patterns, and revealed that making slits with open ends on the ground patterns in parallel with the traces can reduce the conducted noise currents. It was also discovered that the noise currents from PCBs can be suppressed even if the size of the return ground is small. Furthermore, we performed finite-difference time-domain (FDTD) simulations, using eight simple two-layer PCB models in which the ground patterns were split into two parts with different widths and one PCB model with a plane ground pattern, and found that cross-talk decreases with widening the width of the ground pattern and has the smallest values at a specific width. In the present study, to confirm the above findings experimentally, we made actual PCB samples according to exactly the same specification as the models used in the FDTD simulation, and measured the cross-talk between the two parallel signal traces with respect to the different widths of ground patterns. The results approximately agreed with the simulation.

UWB diversity performance in correlated lognormal- sum-distributed in-body to on-body channel

Abstract: Ultra wideband (UWB) technology in low band has being attracted considerable attention for high-speed and real-time transmission from inside to outside human body. However, it suffers from large attenuation and shadow fading in human tissues. A diversity technique is expected to provide effective improvement on its communication performance. This study aims to derive an approximate model for correlated in-body to on-body diversity channel and clarify the diversity effect. First, correlated statistical distribution between each two single signals is approximated as a lognormal sum distribution. Then two flexible parameters s1 and s2 in the lognormal sum approximation are optimized to obtain the probability density function (PDF) of the diversity channel. Finally the average bit error rates (BERs) are calculated theoretically to clarify the diversity effect, and its validity is verified by computer simulations.

Link budget analysis of in-body to on-body UWB low band communications for capsule endoscope

Abstract: This paper aims to perform a link budget analysis for a typical application in wireless implant body area networks (BANs), i.e., capsule endoscope. Ultra wideband (UWB) technology is an attractive candidate for wireless body area communications, especially for providing a high data rate to fulfill real time transmission. In this study, based on the channel characterization and average bit error rate (BER) evaluation results in pulse position modulation (PPM) or on-off keying modulation impulse radio (IR) UWB system over in-body to on-body communication channel, system margin on both single fading channel and two-branch diversity channel are firstly derived and compared, then the link parameters including the communication distance, data rate as well as required transmit power are discussed to clarify the link budget improvement with adoption of diversity reception technique.

Electromagnetic Fields Measurement and Safety Consideration in Magnetic Confinement Fusion Test Facilities

Abstract: The environmental electromagnetic fields were measured around a magnetic confinement fusion test facility namely Large Helical Device (LHD) which is equipped with large superconducting magnet coils system and high-power plasma heating systems of Neutral Beam Injection, Electron Cyclotron resonance Heating and Ion Cyclotron Range of Frequencies (ICRF) heating. The leakage of the static magnetic field from the LHD was less than 1.2 mT, and it varied according to the coil operation. The extremely low frequency electromagnetic field was measured around power supply units for the coil system, and the magnetic field of higher than the guideline level of the International Commission on Nonionizing Radiation Protection (ICNIRP) was predicted. Leakage of high frequency electromagnetic field from the ICRF was observed in bursts according to plasma shots. The measured values were less than the occupational guideline levels. Although the electromagnetic fields were less than the regulation levels, more monitoring survey is necessary from the view point of occupational safety.

Performance test of personal RF monitor for area monitoring at magnetic confinement fusion facility.

Abstract: For safety management at a magnetic confinement fusion-test facility, protection from not only ionising radiation, but also non-ionising radiation such as the leakage of static magnetic and electromagnetic fields is an important issue. Accordingly, the use of a commercially available personal RF monitor for multipoint area monitoring is proposed. In this study, the performance of both fast- and slow-type personal RF monitors was investigated by using a transverse electromagnetic cell system. The range of target frequencies was between 10 and 300 MHz, corresponding to the ion cyclotron range of frequency in a fusion device. The personal RF monitor was found to have good linearity, frequency dependence and isotropic response. However, the time constant for the electric field sensor of the slow-type monitor was much longer than that for the fast-type monitor. Considering the time-varying field at the facility, it is found that the fast-type monitor is suitable for multipoint monitoring at magnetic confinement fusion test facilities.

SAR reduction in implant body area networks with spatial diversity reception

Abstract: This paper investigates the impact of spatial diversity reception on specific absorption rate (SAR) reduction 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 BAN channel modeling with a numerical human body model. Then, we calculate the local peak SAR under the required transmit power when the implant transmitter moves along the digestive organs. Consequently, our simulation results demonstrate that the use of spatial diversity reception can significantly reduce SAR in implant body area networks.

Two whole-body exposure systems for biological effect test of RF electromagnetic fields

Abstract: This paper describes two whole-body exposure systems for biological effect tests of radio frequency (RF) electromagnetic fields. The first exposure system is designed at 2 GHz band to have a feature of circular polarization for simulating a variety of coupling with humans in daily environment. The second exposure system is designed to simulate a multiple-frequency exposure between 800 MHz and 5.5 GHz. In order to get an accurate evaluation on the exposure level for rats in the exposure systems, we developed a statistical analysis tool in our systems. We first took documentary photos of rat activity in the exposure box in a real time. Then we derived the frequency of rats staying in various positions in the exposure box. Using the stay frequency as a weighting factor, we can calculate the whole-body average SAR statistical characteristics during the exposure period. The developed systems and demonstrated performances have shown their high quality and convenience as an exposure system for the above biological effect tests.

Measurement and hemodialysis effect of complex relative permittivity for blood of kidney patients using open‐ended coaxial measurement probe

Abstract: Before evaluating the quality of hemodialysis from the limited volume of human blood using a commercially available open-ended coaxial probe, we previously measured the complex relative permittivity of pure water from 200 MHz to 6 GHz with respect to its measured liquid volume, and found that 1.9 ml of water in a beaker with a diameter of 24 mm and a depth of 2 mm gives a variation within ± 0.5% for the real part and ± 7% for the imaginary part. Based on the above finding, we measured the dielectric properties of 2.5 ml whole blood at 25 °C for 10 normal healthy subjects and 9 hemodialysis patients. The measured results on healthy subjects show good agreement with the data reported by Gabriel for human blood at 37 °C, while they provide different dispersion characteristics of straight lines for their Cole–Cole plots. The measured results on the patients give further different dispersion characteristics versus the healthy subjects. In an investigation of the above differences statistically, Student's t-test revealed that the permittivity at infinite frequency for the Cole–Cole plots is significantly different with a level of 1% among its averaged values for normal healthy subjects and patients before dialysis. © 2012 Wiley Periodicals, Inc. Electron Comm Jpn, 95(12): 56–61, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11421