## 2 Technical Enablers
### Deploying Low-Power Long-Range Networks  
An essential part of smart grid infrastructure is wireless networking protocols and the underlying technologies used for interconnecting smart meters, the network backbone and cloud services deployed over the Internet. Several wireless communication technologies have been proposed during the previous years to facilitate communication within a smart city deployment. These networking technologies mainly focus on increasing network throughput instead of reducing power consumption [65]. More recently, various networking technologies have been proposed that focus on wireless low-power transmissions, such as IEEE 802.15.4 (ZigBee, Z-Wave) and IEEE 802.15.11 (Bluetooth, BLE) [66]. When it comes to smart water metering devices, the Open Meter Standard (OMS) Wireless M-Bus protocol was designed to accommodate specialized industry-grade deployments, operating at the 169 and 868 MHz Industrial, Scientific and Medical (ISM) frequencies [67], with adequately high bit rate exchange capability in a short range. Due to the combination of low-power and short-range operational design, large-sized network deployment requires the combination of protocols that follow the multi-path approach [68] to achieve seamless and error-free message delivery. This approach provides a series of benefits like the ability to overcome obstacles in communication [69; 70] and, most importantly, enhanced network security [71]. However, recent trials carried out in real-world wireless sensor networks have highlighted certain difficulties and limitations of the multi-hop, short-range connectivity paradigm [72]. Thus said, a series of alternative solutions was proposed specifically to mitigate these limitations, for instance deploying nodes with different transmission ranges [70], enforcing a hierarchical network structure [73] or using dedicated mobile nodes for managing the network [74]. Unfortunately, all these efforts to overcome the difficulties of the reduced transmission range of communication interfaces result in complex real-world deployments that span over multiple networking technologies in order to provide urban-scale coverage [75; 76]. Exploiting sub-GHz communication bands, which allow transmission over longer distances, paired with very low data transmission rates, has been the most recent proposition to enable a significant decrease in power consumption [77] and reduce the complexity of urban-scale deployments. Such communication technologies are referred to as Low-Power Wide Area Networks (LPWANs) as opposed to other short-range high-frequency communication bands. Low-frequency signals are significantly less attenuated by multi-path propagation or physical obstacles compared to the high-frequency ones, thus increasing both signal reliability and robustness [69; 78; 79; 80]. In LPWAN, concentrators (also called a collector) play an important role by collecting information from all embedded devices located several kilometres away. LPWANs provide huge benefits for IoTdeployments, including higher autonomy due to lower energy requirements and deployment costs as only a few concentrators can cover large geographical areas [26; 78]. LPWAN communication is based on proprietary modulation techniques that have evolved from the Chirp Spread Spectrum (CSS) and operate in the sub-GHz bands. This allows for independent and asynchronous communication between nodes, partially resembling an ALOHA protocol, that result in an LPWAN concentrator capable of receiving data originating from multiple IoT devices and thus increasing the density of nodes in an LPWAN. Alas, due to unlicensed sub-GHz bands' regulation restrictions, LPWAN may end up in an asymmetric situation with concentrators directly connected to many IoT devices being somehow compromised in terms of functionality compared to less central concentrators connected to only a handful of IoT nodes.