Wireless Body Area Network Communication Research Articles

An ultra-low-power RF transceiver for WBANs in medical applications

A 2.4 GHz ultra-low-power RF transceiver with a 900 MHz auxiliary wake-up link for wireless body area networks (WBANs) in medical applications is presented. The RF transceiver with an asymmetric architecture is proposed to achieve high energy efficiency according to the asymmetric communication in WBANs. The transceiver consists of a main receiver (RX) with an ultra-low-power free-running ring oscillator and a high speed main transmitter (TX) with fast lock-in PLL. A passive wake-up receiver (WuRx) for wake-up function with a high power conversion efficiency (PCE) CMOS rectifier is designed to offer the sensor node the capability of work-on-demand with zero standby power. The chip is implemented in a 0.18 μm CMOS process. Its core area is 1.6 mm2. The main RX achieves a sensitivity of −55 dBm at a 100 kbps OOK data rate while consuming just 210 μA current from the 1 V power supply. The main TX achieves +3 dBm output power with a 4 Mbps/500 kbps/200 kbps data rate for OOK/4 FSK/2 FSK modulation and dissipates 3.25 mA/6.5 mA/6.5 mA current from a 1.8 V power supply. The minimum detectable RF input energy for the wake-up RX is −15 dBm and the PCE is more than 25%.

Trust Key Management Scheme for Wireless Body Area Networks

With recent advances in wireless sensor networks and embedded computing technologies, miniaturized pervasive health monitoring devices have become practically feasible. In addition to providing continuous monitoring and analysis of physiological parameters, the recently pro- posed Wireless Body Area Networks (WBAN) incorporates context aware sensing for increased sensitivity and specificity. A number of tiny wireless sensors, strategically placed on the human body, create a WBAN that can monitor various vital signs, providing real-time feed-back to the user and medical personnel. The wireless body area networks promise to revolutionize health monitoring. Since the sensors collect personal medical data, security and privacy are important components in this kind of networks. It is a challenge to implement traditional security infrastructures in these types of lightweight networks, since they are by design limited in both computational and communication resources. A key enabling technology for secure communications in WBANs has emerged to be biometrics. In this paper, we present an approach that exploits physiological signals (electrocardiogram (ECG)) to address security issues in WBAN: a Trust Key Management Scheme for Wireless Body Area Network. This approach manages the generation and distribution of symmetric cryptographic keys to constituent sensors in a WBAN (using ECG signal) and protects the privacy.

UWB signal propagation at the human head

Among different wireless solutions, ultra-wideband (UWB) communication is one promising transmission technology for wireless body area networks (WBANs). To optimize receiver structures and antennas for UWB WBANs with respect to energy efficiency and complexity, the distinct features of the body area network channel have to be considered. Thus, it is necessary to know the propagation mechanisms in the proximity of the human body. In this paper, we limit ourselves to transmission at the head, since the most important human communication organs, such as the mouth, eyes, and ears, are located there. We especially focus on the link between both ears and consider direct transmission, surface waves, reflections, and diffraction as possible propagation mechanisms. We show theoretically and by measurements, which were performed in the frequency range between 1.5-8 GHz, that direct transmission through the head is negligible due to the strong attenuation. We conclude by process of elimination that diffraction is the main propagation mechanism around the human body and verify these conclusions using a finite-difference time-domain simulation. Based on a second measurement campaign, we derive an approximation of the average power delay profile for the ear-to-ear link and calculate values for mean excess delay and delay spread. Finally, we briefly discuss the impact of the distinct ear-to-ear channel characteristic on the design of a WBAN communication system.