# Moving Towards Body-to-Body Sensor Networks for Ubiquitous Applications: A Survey
## 4 BBN Design Challenges and Open Issues
### Wireless Channel Propagation
#### 4.1.2 BBN Users in Movement
* Rotation movements significantly alter the average signal level (up to 50 dB attenuation), especially when the person turns on the spot and obstructs the LOS position with the other person. * During tilt movements, the received signal is as much impacted as the vicinity between the two persons is reduced. * Finally, in LOS and NLOS walking situations, when one person starts moving during the body-to-body signal propagation, body shadowing and path loss components increase in comparison to stationary scenarios. In outdoor mobile communication channels, the small-scale fading is modeled by a Rayleigh fading, which is defined as the sum of the different scattered signals, due to the surrounding obstacles, received with arbitrary amplitudes. Whereas in BBNs, on-body reflection or direct communication link could give rise to a dominant signal component. Thus the fading component \(X_{SM}\) is assimilated to the Ricean fading, with the Ricean-K factor \(K=A^{2}/2s^{2}\), where \(A\) is the dominant component and \(2s^{2}\) is the average scattered power. Indoor measurements have also been performed in [85], where the \begin{table}
\begin{tabular}{l c c c c c c c} \hline
**Protocol** & **Energy-eff.** & **Reliability** & **QoS** & **Mobility** & **Security** & **Intra-WBAN** & **Inter-WBAN** \\ \hline EAADDV [49] & ✓ & & ✓ & ✓ & & ✓ & \\ \hline SIMPLE [51] & ✓ & ✓ & & & & ✓ & \\ \hline EERS [53] & ✓ & ✓ & & & & ✓ & \\ \hline M-ATTEMPT [50] & ✓ & & ✓ & ✓ & ✓ & ✓ & \\ \hline EAWD [55] & ✓ & ✓ & & ✓ & ✓ & ✓ & \\ \hline CLDO [56] & ✓ & ✓ & ✓ & & & ✓ & \\ \hline AAT [57] & ✓ & ✓ & ✓ & & & ✓ & \\ \hline MoBAN [71] & & & & ✓ & ✓ & ✓ & ✓ \\ \hline McMAC [63] & ✓ & ✓ & ✓ & ✓ & & ✓ & \\ \hline LRPD [61] & & ✓ & ✓ & ✓ & ✓ & ✓ & \\ \hline QPRR [59] & & ✓ & ✓ & & & ✓ & \\ \hline ZEQoS [40] & ✓ & ✓ & ✓ & & & ✓ & ✓ \\ \hline RACOON [65] & & ✓ & & ✓ & & ✓ & ✓ \\ \hline PSR [68] & & ✓ & & ✓ & ✓ & ✓ & \\ \hline MHRP [69] & ✓ & ✓ & ✓ & ✓ & & ✓ & \\ \hline MTR [72] & ✓ & ✓ & & ✓ & & ✓ & \\ \hline CCS [73] & ✓ & & & & ✓ & ✓ & ✓ \\ \hline MobiHealth [79] & & ✓ & ✓ & ✓ & ✓ & ✓ & \\ \hline Hybrid Security Mechanism [74] & & & & & ✓ & ✓ & ✓ \\ \hline Cluster-based sec. mechanism [75] & & & & ✓ & ✓ & ✓ & ✓ \\ \hline \end{tabular}
\end{table} 
Table 3: Comparison of existing wireless body area network (WBAN) solutions to be extended to the BBN environment. © [2019] IEEE. Reprinted and modified, with permission, from [4]. fading envelope was associated to the walking LOS/NLOS scenarios and assimilated to a Nakagami distribution, which is described by the couple of parameters: the shape (\(\mu\)) and the spread (\(\omega\)) [88]. The body shadowing effect was considered for the rotation scenarios performed at different distances separating two WBANs from each other, and top loaded monopole (TLM) antennas have been proved to be less affected by body shadowing, in indoor environments, than other types of body antennas, such as wideband planar monopole (PM) antennas, that have also been considered in the channel measurement campaign of [85]. The different signal propagation BBN scenarios for outdoor and indoor environments are reported, respectively, in Tables 4 and 5, with the corresponding fading components, represented by the Ricean K-factor (\(A\) and \(s\) parameters) for outdoor scenarios and Nakagami parameters for the indoor environment. The shadowing (\(X_{BS}\)) is represented, for the outdoor signal, by the \(\mu\) and \(\sigma\) parameters of the lognormal probability distribution function (PDF). The shadowing standard deviation \(\sigma_{s}\) characterizes the shadowing component for the indoor rotation scenario. We have reported those results for TLM antennas considering the scenarios described by Figure 7. It is worth to note that [PERSON] et al.