## 5 Conclusions and Perspectives  
To conclude, with reference to wearable wireless network end-to-end connectivity, we highlighted the key envisioned challenges. First, while operating at low transmission power and under realistic conditions, the packet reception performance can be significantly degraded while exploiting the BAN-specific IEEE 802.15.6 standard. Second, the routing approach and the dissemination strategy have an impact on the end-to-end connectivity and the end-to-end round-trip time delay. It is concluded also, for an indoor scenario with the considered settings, that the BBN average disconnections are higher than 43% within 4 hops. Third, it is observed that wireless standard (i.e., WiFi IEEE 802.11n), while having a large coverage support, it is not entirely appropriate for BBN communications in indoor propagation as it has a very high average of end-to-end disconnections.  
For the future, it is necessary to investigate other wireless body-to-body communication technologies. Indeed, WiFi IEEE 802.11 ac standards, as well as cellular technologies Long-Term  
Figure 7: Average disconnections and round-trip time delay per hop count for WBAN (android smart phone mobile node with ORACE-Net protocol-enabled) in an indoor scenario.  
Evolution (LTE)/5G could potentially fulfill operational BBN requirements (especially regarding range and connectivity). Furthermore, the IEEE 802.11 ac standard uses a 5-GHz frequency which avoids most of the interference possibilities and with the provision of higher number of channels defined by the standard (i.e., 25 channels by considering a channel width equal to 20 MHz) could be interesting to investigate. In addition, 4G/LTE is also another ubiquitous approach followed by 5G to deliver an edge-free body-to-body experience. Besides, specific technologies targeting the IoT could offer connectivity at various network tiers. LTE Cat M1 Machine Type Communications (eMTC), LTE CAT NB1 Narrowband Internet of Things(NB-IoT), and 802.11 ah (WiFi HaLow) are such candidate technologies for which chipsets are known to exist or have been announced. Table 4 highlights a selection of such chipsets. Their availability or future availability paves the way for further investigations and modeling related to their longer range connectivity, reliability, etc. Most of these standards are designed to consume much less power than classical cellular technologies and therefore could prove very effective in future wearable wireless networks.  
**Acknowledgments:** This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 668995. This material reflects only the authors view and the EC Research Executive Agency is not responsible for any use that may be made of the information it contains.  
**Author Contributions:** This paper was prepared through the collective efforts of all authors. In particular, [PERSON] prepared the manuscript based on the suggestions and guidance of [PERSON]. [PERSON] made substantial contributions towards overall writing, organization, and presentation of the paper. He also conducted the experiment based on which results are discussed. In particular, he contributed in introduction, body-to-body communications: technologies, routing and challenges. He also detailed the experiment scenario and discussed the achieved results. [PERSON] introduced the scope of the paper within the abstract, then presented the on-body technologies and connectivity challenges with regards to IEEE 802.15.6 standards. [PERSON] presented the different current implementations of human body communications. He also provided an overview on the future technologies with regards to the IoT trends. [PERSON] made contributions to the literature research and paper writing. [PERSON], [PERSON] also did a critical revision of the paper and provided detailed feedback to improve the manuscript content. All authors have read and approved the final manuscript.  
**Conflicts of Interest:** The authors declare no conflict of interest.