## 5 Conclusions  
In this paper we have proposed a novel routing framework for wireless multi-hop networks, which considers minimizing the exposure to Electromagnetic Fields, leveraging  
Figure 14: CCDF of the power transmitted by each node. (a) 50 intermediate nodes. (b) 200 intermediate nodes.  
Figure 15: Random topology: power transmission statistics. (a) Average transmitted power. (b) Total transmitted power.  
an original and novel approach for these scenarios. In the last years we have observed a growing concern regarding the effects that EMF induced by wireless communications may have over people. Indeed, this concern has increased with the appearance of novel wireless technologies for 5G systems, such as mmWave. In order to address this, we have proposed an EMF-aware solution that can be used in multi-hop wireless networks, such as the ones used for D2D or WSN for Internet of Things (IoT).  
We have carried out a holistic approach, combining both theoretical and simulation-based analysis. First, we studied the optimum performance by means of a novel algorithm based on graph theory. Afterwards, taking into account that the exposure cannot be directly embedded within a routing protocol, we have presented an analytical model of the exposure, where we identified a sensible metric that could be used in order to effectively reduce the exposure. Afterwards, we have presented the design and specification of a routing protocol that tackles the exposure reduction, and we assessed its performance by means of an extensive simulation campaign.  
The results offer the evidence that the proposed solutions (both the algorithm and the protocol) are able to fairly balance the EMF exposure within the network, also yielding a decrease on the average exposure. We have also seen that the observed gain is more relevant for higher node densities, since the proposed approach benefits from a larger number of alternative paths. In addition, the analysis evinces that there is not a relevant trade-off in terms of the consumed power, and our solution roughly keeps the overall transmit power as the one that minimizes this particular metric. Moreover, the evaluation results show that the use of the dynamic cost that accounts for the accumulated exposure brings remarkable benefits, by reducing the average emitted power. On top of it, the same benefits can be observed in the overall transmitted power by the network. This reduction is obtained thanks to the fair distribution of the exposure induced by different nodes and so a better traffic balance among alternative paths.  
In our future work, we will study the proposed scheme over more dynamic (adding mobility) and complex (with higher densities) scenarios. We will also look at the weights given to the two parameters, and their impact over the algorithm/protocol performance, assessing whether there is any optimum configuration that might yield better performances.  
Conceptualization, V.I, L.D., E.S. and R.A.; methodology, V.I. and L.D.; software, L.D.; formal analysis, V.I.; writing--original draft preparation, V.I. and L.D.; writing--review and editing, V.I., L.D., E.S. and R.A.; funding acquisition, E.S., R.A. All authors have read and agreed to the published version of the manuscript.  
This work has received funding from the Spanish Government (Ministerio de Economia y Competitividad, Fondo Europeo de Desarrollo Regional, MINECO-FEDER) by means of the project FIERCE: Future Internet Enabled Resilient smart CitiEs (RTI2018-093475-A100).  
Not applicable.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} NS-3 & Network Simulator 3 \\ D2D & device-to-device \\ QoS & Quality of Service \\ AODV & Ad hoc On-Demand Distance Vector Routing \\ EA-AODV & EMF Aware AODV \\ CCA & Cycle Canceling Algorithm \\ \end{tabular}