Abstract
Ultrawideband (UWB) communication is a promising technology for wireless body area networks (BANs), especially for applications that require transmission of both low and high data rates with excellent energy efficiency. Therefore, understanding the unique UWB channel propagation characteristics around the human body is critical for a successful wireless system, especially for insuring the reliability of important vital sign data. Previous work has focused only on on-body channels, where both TX and RX antennas are located on the human body. In this paper, a 3–5 GHz UWB channel is measured and analyzed for human body wireless communications. Beyond the conventional on-body channel model, line-of-sight (LOS) and non-line-of-sight (NLOS) channel models are obtained using a TX antenna placed at various locations of the human body while the RX antenna is placed away from the human body. Measurement results indicate that the human body does not significantly degrade the impedance of a monopole omnidirectional antenna. The measured path loss and multipath analysis suggest that a LOS UWB channel is excellent for low-power, high-data-rate transmission, while NLOS and on-body channels need to be reconfigured to operate at a lower data rate due to high path loss.
Highlights
There has been an increased interest in using body area networks (BANs) for health monitoring [1,2,3,4,5,6,7]
We present a complete UWB channel model that considers on-body UWB propagation and extends to include LOS and NLOS channel measurement, using a TX antenna placed on the human body and a separate RX antenna located externally
A vector network analyzer (VNA) is employed that captures the frequency response of the UWB channel as a S21 parameter, followed by generation of a channel impulse response (CIR) in the time domain, obtained by performing an inverse Fourier transform (IFT)
Summary
There has been an increased interest in using body area networks (BANs) for health monitoring [1,2,3,4,5,6,7]. The sensor captures the real-time physiological signals, activating the transmitter that sends a low-data-rate signal to the receiver alerting a remote clinician through cellular or internet networks. Unlike these traditional narrowband systems, ultrawideband (UWB) wireless sensors operate with a large bandwidth (3.1– 10.6 GHz) and a low maximum transmission spectral density (−41.3 dBm/MHz). Molisch et al [9] developed an IEEE 802.15.4a channel model for various low-rate UWB applications, where the body area network channel model is analyzed using a finite difference timedomain (FDTD) simulator with antennas moving around the human body.
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