The Internet of Bodies: A Systematic Survey on Propagation
Characterization and Channel Modeling
Abstract
The Internet of Bodies (IoB) is an imminent extension to the vast
Internet of things domain, where interconnected devices (e.g., worn,
implanted, embedded, swallowed, etc.) located in-on-and-around the human
body form a network. Thus, the IoB can enable a myriad of services and
applications for a wide range of sectors, including medicine, safety,
security, wellness, entertainment, to name but a few. Especially
considering the recent health and economic crisis caused by novel
coronavirus pandemic, a.k.a. COVID-19, the IoB can revolutionize today’s
public health and safety infrastructure. Nonetheless, reaping the full
benefit of IoB is still subject to addressing related risks, concerns,
and challenges. Hence, this survey first outlines the IoB requirements
and related communication and networking standards. Considering the
lossy and heterogeneous dielectric properties of the human body, one of
the major technical challenges is characterizing the behavior of the
communication links in-on-and-around the human body. Therefore, this
paper presents a systematic survey of channel modeling issues for
various link types of human body communication (HBC) channels below 100
MHz, the narrowband (NB) channels between 400 MHz and 2.5 GHz, and
ultra-wideband (UWB) channels from 3 to 10 GHz. After explaining
bio-electromagnetics attributes of the human body, physical and
numerical body phantoms are presented along with electromagnetic
propagation tool models. Then, the first-order (i.e., path loss,
shadowing, multipath fading) and the second-order (i.e., delay spread,
power delay profile, average fade duration, level crossing rate, etc.)
channel statistics for NB and UWB channels are covered with a special
emphasis on body posture, mobility, and antenna effects. For the HBC
channels, three different coupling methods are considered: capacitive,
galvanic, and magnetic. Based on these coupling methods, four different
channel modeling methods (i.e., analytical, numerical, circuit, and
empirical) are investigated, and electrode effects are discussed.
Lastly, interested readers are provided with open research challenges
and potential future research directions.