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To realize implant communications with a high data rate, ultra-wideband (UWB) transmission has gathered a lot of attention as a promising candidate. However, due to high operation frequency, the UWB communication link suffers from large attenuation. This represents the difficulty to achieve reliable communications. To mitigate such a problem, spatial diversity techniques have been proposed in the literature, where some of them work without any frequency extension. In contrast, the implant side diversity technique has been rarely discussed because of the difficulty in miniaturizing the size of the transmitter antenna. In this paper, we designed a UWB transmitter diversity antenna and evaluated its performance numerically and experimentally. First, we analyzed the antenna performance using a finite-difference time-domain simulation and physical experiment in a liquid phantom. Thereafter, we measured the path loss performance in an implant communication link using a liquid phantom and a living porcine subject. Finally, we evaluated the impact of the implant side polarization diversity system with the developed antenna on the communication performance. Based on the measured isolation between the polarization channels, our measurements show that a signal-to-noise power ratio improvement of 7 dB can be in principle achieved with a predicted outage rate of 0.01 and a range of 15 cm in typical body environments. [ABSTRACT FROM PUBLISHER]

Ultrawideband (UWB) radio technology for wireless implants has gained significant attention. UWB enables the fabrication of faster and smaller transceivers with ultralow power consumption, which may be integrated into more sophisticated implantable biomedical sensors and actuators. Nevertheless, the large path loss suffered by UWB signals propagating through inhomogeneous layers of biological tissues is a major hindering factor. For the optimal design of implantable transceivers, the accurate characterization of the UWB radio propagation in living biological tissues is indispensable. Channel measurements in phantoms and numerical simulations with digital anatomical models provide good initial insight into the expected path loss in complex propagation media like the human body, but they often fail to capture the effects of blood circulation, respiration, and temperature gradients of a living subject. Therefore, we performed UWB channel measurements within 1–6 GHz on two living porcine subjects because of the anatomical resemblance with an average human torso. We present for the first time, a path loss model derived from these in vivo measurements, which includes the frequency-dependent attenuation. The use of multiple on-body receiving antennas to combat the high propagation losses in implant radio channels was also investigated. [ABSTRACT FROM PUBLISHER]

Biomedical implantable sensors transmitting a variety of physiological signals have been proven very useful in the management of chronic diseases. Currently, the vast majority of these in-body wireless sensors communicate in frequencies below 1 GHz. Although the radio propagation losses through biological tissues may be lower in such frequencies, e.g., the medical implant communication services band of 402 to 405 MHz, the maximal channel bandwidths allowed therein constrain the implantable devices to low data rate transmissions. Novel and more sophisticated wireless in-body sensors and actuators may require higher data rate communication interfaces. Therefore, the radio spectrum above 1 GHz for the use of wearable medical sensing applications should be considered for in-body applications too. Wider channel bandwidths and smaller antenna sizes may be obtained in frequency bands above 1 GHz at the expense of larger propagation losses. Therefore, in this paper, we present a phantom-based radio propagation study for the frequency bands of 2360 to 2400 MHz, which has been set aside for wearable body area network nodes, and the industrial, scientific, medical band of 2400 to 2483.5 MHz. Three different channel scenarios were considered for the propagation measurements: in-body to in-body, in-body to on-body, and in-body to off-body. We provide for the first time path loss formulas for all these cases. [ABSTRACT FROM PUBLISHER]

In the last decade, the utilization of radio technology for a variety of clinical and medical applications has increased dramatically. Advances in microelectronics have enabled the miniaturization and integration of biomedical sensors and radio transceivers into single units. Such wireless sensors can be worn or implanted, and they facilitate the continuous collection and transmission of physiological signals. The centrally coordinated or distributed interconnection of wireless biomedical sensors, referred to as a body area network (BAN), has already been standardized in IEEE Standard 802.15.6-2012. Besides narrowband (NB), IEEE Standard 802.15.6-2012 supports the use of ultrawideband (UWB) radio interfaces for wearable sensors. The U.S. Federal Communications Commission (FCC) defines UWB signals to be those with fractional bandwidth exceeding 20% of the center frequency, or alternatively, a bandwidth greater than 500 MHz. A number of techniques can be used to generate UWB signals; the most widely used is the one referred to as impulse radio (IR) and consists of transmitting very narrow pulses in the time domain, commonly in the order of a few nanoseconds with fast rise times reaching 50 ps [1]. Another common approach to generate UWB signals is subcarrier aggregation in orthogonal frequency-domain multiplexing (OFDM), which is generally used for short-range nonmedical indoor communications. The very large bandwidth enables high-data-rate communications. In the presence of noise and power constraints, UWB allows trading a section of the ?bandwidth for power according to the Shannon?Hartley theorem. This means UWB communication systems can operate with ultralow power and low signal-to-noise ratio (SNR) using different modulation and coding strategies. UWB signals have other inherent characteristics that make them suitable for the wireless interface of wearable biomedical sensors. Noiselike behavior due to the extremely low maximal effective isotropically radiated power (EIRP) spectral density of ?41.3 dBm/MHz makes UWB signals difficult to detect by NB systems and robust against jamming, potentially rescinding the need for complex encryption algorithms. Additionally, UWB signals do not represent a threat to patients? safety [2]. Much research has been done toward the use of BAN technology for ubiquitous monitoring of patients suffering from chronic diseases. Nevertheless, the commercial use of UWB for BAN has been limited in part by the FCC regulations, which restrict the communication applications to 3.1?10.6 GHz where propagation conditions in the body environment are rather unfavorable. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM PUBLISHER]

Wearable wireless medical sensors beneficially impact the healthcare sector, and this market is experiencing rapid growth. In the United States alone, the telecommunications services market for the healthcare sector is forecast to increase from $7.5 billion in 2008 to $11.3 billion in 2013. Medical body area networks improve the mobility of patients and medical personnel during surgery, accelerate the patients? recovery, and facilitate the remote monitoring of patients suffering from chronic diseases. Currently, MBANs are being introduced in unlicensed frequency bands, where the risk of mutual interference with other electronic devices can be high. Techniques developed during the evolution of cognitive radio can potentially alleviate these problems in medical communication environments. In addition, these techniques can help increase the efficiency of spectrum usage to accommodate the rapidly growing demand for wireless MBAN solutions and enhance coexistence with other collocated wireless systems. This article proposes a viable architecture of an MBAN with practical CR features based on ultra wideband radio technology. UWB signals offer many advantages to MBANs, and some features of this technology can be exploited for effective implementation of CR. We discuss the physical and MAC layer aspects of the proposal in addition to the implementation challenges. [ABSTRACT FROM PUBLISHER]

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 TG15.6 in December 2007. As a result of more than four years of effort, in February 2012, TG15.6 published the first international standard for BANs, IEEE Std 802.15.6. 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 802.15.6 through the use of ultra wideband signals for implantable devices along with physical measurements in animals is also presented. [ABSTRACT FROM AUTHOR]