Showing papers by "Jianqing Wang published in 2014"

Experimental Evaluation of Implant UWB-IR Transmission With Living Animal for Body Area Networks

Abstract: One of promising transmission technologies in wireless body area networks (BANs) is ultra-wideband (UWB) communication, which can provide high data rate for real-time transmission, and extremely low power consumption for increasing device longevity. However, UWB signals suffer from large attenuation in a wireless communication link, especially in implant BANs. Although several investigations on channel characterization have been far thus conducted for evaluating the UWB transmission performance, they have been limited to either computer simulations or experiments with biological-equivalent phantoms. Experimental evaluation with a living body has rarely been conducted, i.e., the performance in real implant BANs has been scarcely discussed. In this paper, therefore, we focus on a living animal experimental evaluation on the UWB transmission performance. To begin with, we develop an ultra-wideband impulse radio (UWB-IR) communication system with a multipulse pulse position modulation scheme, and then analyze the fundamental characteristics of the developed UWB-IR communication system by a liquid phantom experiment. Finally, we evaluate the performance of the developed UWB-IR communication system via the living animal experiment. From the experimental results, although we have observed that the path loss is more than 80 dB, the developed system can achieve a bit error rate of 10-2 within the communication distance of 120 mm with ensuring a high data rate of 1 Mb/s. This result first time gives a quantitative communication performance evaluation for the implant UWB transmission in a living body.

A Hybrid MoM/FDTD Method for Dosimetry of Small Animal in Reverberation Chamber

Abstract: A hybrid approach combining the method of moment (MoM) and the finite-difference time-domain (FDTD) method is applied to a problem of evaluating specific absorption rates (SARs) in a small rat inside a reverberation chamber (RC). The hybrid method is an alternative technique used to overcome the problem of poor convergence for a solution of the FDTD method in analyzing the RC. First, the RC with a dipole or a helical antenna is designed numerically to function properly at 2 GHz. Then, the MoM/FDTD method is used to calculate the whole-body average SAR (WBA-SAR) for a small animal inside an open cavity. The results are compared with those obtained with the FDTD method in order to verify accuracy. The SAR distributions when stirrers are rotating are also determined. Finally, it is numerically found that the ratio of the WBA-SAR of the 118 g rat to the mean squared electric field is 0.149 (mW/kg)/(V/m) $^{2}$ and an input antenna power of 2.2 W is required to produce a WBA-SAR of 4 W/kg for our designed chamber.

Novel joint TOA/RSSI-based WCE location tracking method without prior knowledge of biological human body tissues.

Abstract: This paper proposes a novel joint time of arrival (TOA)/received signal strength indicator (RSSI)-based wireless capsule endoscope (WCE) location tracking method without prior knowledge of biological human tissues. Generally, TOA-based localization can achieve much higher localization accuracy than other radio frequency-based localization techniques, whereas wireless signals transmitted from a WCE pass through various kinds of human body tissues, as a result, the propagation velocity inside a human body should be different from one in free space. Because the variation of propagation velocity is mainly affected by the relative permittivity of human body tissues, instead of pre-measurement for the relative permittivity in advance, we simultaneously estimate not only the WCE location but also the relative permittivity information. For this purpose, this paper first derives the relative permittivity estimation model with measured RSSI information. Then, we pay attention to a particle filter algorithm with the TOA-based localization and the RSSI-based relative permittivity estimation. Our computer simulation results demonstrates that the proposed tracking methods with the particle filter can accomplish an excellent localization accuracy of around 2 mm without prior information of the relative permittivity of the human body tissues.

Multigenerational effects of whole body exposure to 2.14 GHz W-CDMA cellular phone signals on brain function in rats.

Abstract: The present experimental study was carried out with rats to evaluate the effects of whole body exposure to 2.14 GHz band code division multiple access (W-CDMA) signals for 20 h a day, over three generations. The average specific absorption rate (SAR, in unit of W/kg) for dams was designed at three levels: high (<0.24 W/kg), low (<0.08 W/kg), and 0 (sham exposure). Pregnant mothers (4 rats/group) were exposed from gestational day (GD) 7 to weaning and then their offspring (F1 generation, 4 males and 4 females/dam, respectively) were continuously exposed until 6 weeks of age. The F1 females were mated with F1 males at 11 weeks old, and then starting from GD 7, they were exposed continuously to the electromagnetic field (EMF; one half of the F1 offspring was used for mating, that is, two of each sex per dam and 8 males and 8 females/group, except for all offspring for the functional development tests). This protocol was repeated in the same manner on pregnant F2 females and F3 pups; the latter were killed at 10 weeks of age. No abnormalities were observed in the mother rats (F0, F1, and F2) and in the offspring (F1, F2, and F3) in any biological parameters, including neurobehavioral function. Thus, it was concluded that under the experimental conditions applied, multigenerational whole body exposure to 2.14 GHz W-CDMA signals for 20 h/day did not cause any adverse effects on the F1, F2, and F3 offspring. Bioelectromagnetics. 35:497–511, 2014. © 2014 Wiley Periodicals, Inc.

Quantification and Verification of Whole-Body-Average SARs in Small Animals Exposed to Electromagnetic Fields inside Reverberation Chamber

Abstract: This paper aims to achieve a high-quality exposure level quantification of whole-body average-specific absorption rates (WBASARs) for small animals in a medium-size reverberation chamber (RC). A two-step method, which incorporates the finite-difference time-domain (FDTD) numerical solutions with electric field measurements in an RCtype exposure system, has been used as an evaluation method to determine the whole-body exposure level in small animals. However, there is little data that quantitatively demonstrate the validity and accuracy of this method in an RC up to now. In order to clarify the validity of the twostep method, we compare the physical quantities in terms of electric field strength and WBA-SARs by using a direct numerical assessment method known as the method of moments (MoM) with ten homogenous gel phantoms placed in an RC with 2 GHz exposure. The comparison results show that the relative errors between the two-step method and the MoM approach are approximately below 10%, which reveals the validity and usefulness of the two-step technique. Finally, we perform a dosimetric analysis of the WBA-SARs for anatomical mouse models with the two-step method and determine the input power related to our developed RC-exposure system to achieve a target exposure level in small animals. key words: specific absorption rate (SAR), reverberation-chamber (RC), exposure system, finite-difference time-domain (FDTD) method, method of moments (MoM)

Quantitative Relationship between Whole Body Averaged SARs and Voxel SARs in Numerical Human Models of Pregnant Woman and 3‐Year‐Child for Far‐Field Exposure

Abstract: SUMMARY Safety standards and guidelines for radio-frequency exposure are being set based on whole-body averaged SARs (WBA-SARs) and localized average SARs. In Japan, the WBA-SAR and 1 g localized average SAR are set at 0.4 W/kg and at 8 W/kg, respectively, except for the arms and legs and surface of body. The safety limits of WBA-SARs were determined from observing the behavior destruction of animals for radio-frequency exposure, but those of localized average SARs were determined under the assumption that a spatial peak SAR value does not exceed 20-fold WBA-SARs without their biological evidences. In this paper, to confirm whether or not the above assumption is valid, we calculated WBA-SARs and voxel SARs in the frequency range from 50 MHz to 2 GHz in anatomical-based human numerical models for pregnant woman and 3-year-child for vertically and horizontally polarized far-field exposures, and derived the histogram and cumulative relative frequency of voxel SARs to obtain the quantitative relationship between WBA-SARs and voxel SARs. As a result, we found that 99.90-percentile voxel SARs are not exceeding 20-fold WBA-SARs, while 99.00-percentile voxel SARs are smaller than 10-fold WBA-SARs in both human models.

Performance Evaluation and Link Budget Analysis on Dual-Mode Communication System in Body Area Networks

Abstract: Wireless body area networks (BANs) are attracting great attention as a future technology of wireless networks for healthcare and medical applications. Wireless BANs can generally be divided into two categories, i.e., wearable BANs and implant BANs. However, the performance requirements and channel propagation characteristics of these two kinds of BANs are quite different from each other, that is, wireless signals are approximately transmitted along the human body as a surface wave in wearable BANs, on the other hand, the signals are transmitted through the human tissues in implant BANs. As an effective solution for this problem, this paper first introduces a dual-mode communication system, which is composed of transmitters for in-body and on-body communications and a receiver for both communications. Then, we evaluate the bit error rate (BER) performance of the dual-mode communication system via computer simulations based on realistic channel models, which can reasonably represent the propagation characteristics of on-body and in-body communications. Finally, we conduct a link budget analysis based on the derived BER performances and discuss the link parameters including system margin, maximum link distance, data rate and required transmit power. Our computer simulation results and analysis results demonstrate the feasibility of the dual-mode communication system in wireless BANs. key words: body area networks, dual-mode communication system, bit error rate, link budget

Specific absorption rate reduction based on outage probability analysis for wireless capsule endoscope with spatial receive diversity

Abstract: This study investigates the effect of spatial receive diversity on specific absorption rate (SAR) reduction based on outage probability analysis for wireless capsule endoscope (WCE). The communication performance of WCE depends much on the transmit power, which is strictly regulated in order to satisfy a safety guideline in terms of SAR, whereas WCE requires high communication performance due to its real-time data transmission. For the purpose of SAR reduction for a WCE scenario, the authors pay attention to the expectation that applying spatial diversity reception to WCE systems can not only improve the wireless communication performance but also reduce SAR. To begin with, based on finite-difference time-domain simulations with a numerical human body model, the outage probability is calculated under this implant propagation channel and the required transmit power is derived to secure a permissible outage probability. Then, the local peak SAR is calculated under the required transmit power when the WCE moves through the digestive organs. Finally, the simulation results demonstrate that applying spatial diversity reception can significantly reduce SAR for WCE.

Local frequency offset spatial diversity with pi/4-DQPSK in implant communications

Abstract: Space diversity reception is well known as a technique that can improve the performance of wireless communication systems without any temporal and spectral resource expansion. Implant body area networks (BANs) require low energy consumption and in some cases high-speed transmission. Therefore, applying spatial diversity reception to implant BANs can be expected to fulfill these requirements. For this purpose, this paper presents a local frequency offset diversity system with π/4-differential quadrature phase shift keying (DQPSK) for implant BANs that offer improved communication performance with a simpler receiver structure, and evaluates the proposal's bit error rate (BER) performance. We first confirm that the local frequency offset diversity reception can effectively improve the communication performance of implant BANs. We then perform an analysis of a realistic communication performance, namely, a link budget analysis based on derived BER performance and evaluate the link parameters including system margin and maximum link distance. These results demonstrate that the local frequency offset diversity system can realize a reliable communication link in a realistic implant BAN scenario.

Performance evaluation on FPGA-implemented UWB-IR receiver for in-body to out-of-body communication systems

Abstract: In order to design an optimized transceiver structure of ultra wideband (UWB) transmission in in-body to out-of-body communications, it is necessary to make the transceiver structure be easily adjustable in order to realize a good communication performance in an experimental environment. For this purpose, we first implement our develop UWB-impulse radio (IR) receiver structure for the in-body to out-of-body communication in a field programmable gate array (FPGA) board, and evaluate the fundamental communication performance of the FPGA-implemented UWB-IR receiver by a biological-equivalent liquid phantom experiment. The FPGA configuration results indicate that our FPGA realization of the UWB-IR receiver has accomplished good communication performance with few FPGA slices. Moreover, the evaluation results in the liquid phantom experiment show that the FPGA-implemented UWB-IR receiver can achieve a bit error rate (BER) of 10(-3) up to a communication distance of 70 mm with ensuring a high data rate of 2 Mbps.

Benefits and limits of UWB for In- and out-of-body communication

Abstract: This work investigates the characteristics of the wireless in-body communication channel within the UWB frequency range from 3 GHz to 6 GHz. A series of experiments using a liquid human phantom is carried out in order to determine optimal transmission parameters for compact, high performance ingestible and implantable wireless medical devices. Although suited for low power and high throughput applications, UWB is strongly limited by the high attenuation in tissues in the microwave frequency range. Transmission loss measurements performed with an 11 mm loop antenna and an UWB transceiver prototype confirm this assumption. We therefore suggest using moderately wideband modulation techniques at the lowest frequency end of the UWB range.

EMI evaluation based on electromagnetic and circuit analysis for human body communication systems

Abstract: In this paper, we employed a two-step approach to evaluate the electromagnetic interference (EMI) voltage at cardiac pacemaker from human body communication (HBC) signals. In the first step, we calculated the input voltage of the analogue sensing circuit of pacemaker using an electromagnetic field analysis tool by considering the pacemaker as a receiving antenna. In the second step, we evaluated the output voltage of the sensing circuit via a circuit simulation approach. The results have shown that a part of HBC signals passes through the low-pass filter of the sensing circuit as interference. Moreover, a DC offset component of the operational amplifier (opamp) in the sensing circuit is further added to the high-frequency interference voltages so that the sensing threshold of malfunction is easier to be exceeded. As a result, it is found that there may be a margin at least 25 dB for malfunction of pacemaker under a typical 1-V HBC transmit voltage and the representative sensing circuit configuration.

Effects of the exposure of 2.14GHz W-CDMA radiofrequency electromagnetic fields to rats on body temperature increase and heat shock proteins expression

Abstract: The radio frequency-electromagnetic field (RF-EMF) exposure and heat shock protein (Hsp) expression has been discussed, but there is no data on the relationship between thermal increase by RF-EMF and Hsp expression. Rats were exposed to RF-EMFs [2.14 GHz, wideband-code division multiple access (W-CDMA) signals] for 2 h/day for 3 days or 1 h/day for 10 days with a whole body average-specific absorption rate (WBA-SAR) of 4 W/kg or 0.4 W/kg, respectively. It appeared the intraperitoneal temperature was increased during RF-EMFs exposure and the Hsp27 and Hsp110 genes were significantly upregulated in the cerebral cortex and cerebellum at 4 W/kg, but protein upregulation was not detected. In contrast, there was no significant change in any of the genes at 0.4 W/kg. These results indicated that the thermal increase of the body by RF-EMF exposure plays critical role on Hsp expression.

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.

FPGA implemention of UWB-IR receiver for in-body to out-of-body communication performance evaluation

Abstract: For designing an optimized transceiver structure of ultra wideband (UWB) transmission in in-body to out-of-body communications, it is necessary to make the transceiver structure be easily adjustable in order to realize a good communication performance in an experimental environment. For this purpose, we first implement our develop UWB-impulse radio (IR) receiver structure for the in-body to out-of-body communication in a field programmable gate array (FPGA) board, and evaluate the fundamental performance of the FPGA-implemented UWB-IR receiver by a biological-equivalent liquid phantom experiment. The FPGA configuration results indicate that our FPGA realization of the UWB-IR receiver has accomplished quite few FPGA slices without any communication performance degradation. Moreover, the evaluation result in the liquid phantom experiment shows that the FPGA-implemented UWB-IR receiver can achieve a bit error rate (BER) of 10−3 up to a communication distance of 70 mm with ensuring a high data rate of 2 Mbps.

A case study on ESD immunity test for a small-type control board

Abstract: In conformity with the IEC61000-4-2 standard, we conducted a case study of electrostatic discharge (ESD) tests for a small-type control board to investigate the basic coupling characteristics of induced noises by indirect ESDs. With a vertical coupling metal plane (VCP) and a horizontal coupling metal plane (HCP), the test was conducted under ±4kV and ± 8kV charging voltages. Pulse width modulation (PWM) signal outputs, which were used for controlling a pulse motor, were measured with a digital oscilloscope and were statistically analyzed with respect to their pulse widths. The analyzed results show that the interference from the ESD noises could be divided into two types: the first type is a very short pulse which is caused by the ESD noise itself, while the other one is the induced pulses overlapping on the PWM signals, which are split into several short pulses by the ESD noise. This type noise may result in causing a malfunction of the pulse motor. Furthermore, from the experiment more findings could be derived as follows: Firstly, the main interference from the indirect ESDs is the first type, and the higher charge voltage an ESD gun has, more frequently both types appear. Secondly, no matter which polarity induced noise voltages from the ESD gun have, both types of interference can be observed. Finally, the interference from the HCP is stronger than that from the VCP.