## 2 Related Work  
As discussed in Section 1, we have witnessed, in recent years, an upturn on the research regarding multi-hop topologies. Their original purpose, as emergency scenarios, has led to other innovative applications and use cases. Nowadays, either Wireless SensorNetworks (WSN) or device-to-device (D2D) communications can have a significant impact on the individual exposure of humans, due to the body proximity of the involved devices. Indeed, routing in WSN is still actively investigated for different application use cases related to 5G and beyond 5G. For instance, in [8] the authors propose a novel ad-hoc routing protocol, so-called VARP, specially designed to enhance the performance of 5G wireless networks leveraging D2D capabilities. In addition, depending on the specific targets and scenarios, different methods are applied to solve the routing problem. In this sense, [PERSON] et al. [9] applied genetic algorithms to select the best routing from a set of them in Mobile Ad-hoc Networks (MANET) scenarios, exploiting the On-demand Multipath Distance Vector (AOMDV). Following a different approach, fuzzy Petri nets and ant colony optimization techniques are used in [10] to improve the QoS parameters, such as delivery ratio, throughput, or delay. Similar to the number of methods, the range of application use cases is also very broad. In this regard, the authors of [11] study routing for D2D communications using mmWave technology. Another routing solution in a MANET scenario is presented in [12], as part of a mobile edge computing setup embracing drones. In particular, this work combines data forwarding and task offloading. Similarly, [PERSON] et al. apply in [13] routing over a Vehicular Ad-hoc Networks (VANET) scenario for intelligent transportation systems, as a key service vertical addressed by 5G communication technology. The authors propose a protocol named low-latency and energy efficient routing based on network connectivity (LENC), which is able to outperform legacy solutions. As can be observed from the literature review, routing in multi-hop wireless networks is still a key technique for present and forthcoming use cases. As for routing metrics, they have traditionally focused on QoS parameters, such as delay, hop count, or power [14; 15]. Based on these parameters, the routing metrics can be divided into two main categories [16]: (1) single-radio, and (2) multi-radio. From the single-radio category, the Expected Transmission Count (ETX) [17] and the Expected Transmission Time (ETT) [18] are two of the most widespread alternatives, and they have been enhanced and broadened with the Weighted Cummulative Expected Transmission Time (WCETT) [18], the Exclusive Expected Transmission Time (EETT) [19], or with other solutions that take into consideration the interference phenomenon. The Metric for Interference and Channel Switching (MIC) [20] or the Interference Aware (iAWARE) [21] are examples belonging to the multi-radio category. Somehow related to EMF exposure, Green Networking gathered the attention from the scientific community. The main idea behind it is promoting an energy-aware behavior, mostly by means of reducing the transmitted power, increasing at the same time the battery life-time. Most of the existing proposals [22; 23] deal with cellular communications, while not much attention has been paid to wireless multi-hop topologies. As of today, novel solutions pursue optimizing the same performance parameters, but energy, alone or combined with other criteria, is becoming more relevant. In this regard, [PERSON] et al. propose in [24] a routing technique to trade off energy efficiency and security. Similarly, a joint optimization problem, accounting for power control and routing, is posed and solved, using Benders decomposition, in [25]. The authors focus on the performance of the analytical solution, rather than addressing it from a protocol perspective.