## 2 Conventional Network and the Need for Smart Grids
#### AMI in Microgrids  
Nowadays, there are new devices that are capable of processing information in the electrical sector and that access the Internet or adjust the energy consumption based on cost or availability depending on the preferences of consumers. All of this is part of what is called the Internet of Things (IoT). The \"things\" in SG include sensors [3; 68; 69], smart devices and the SMs [1; 27; 68; 70]. The devices need to be interconnected in a hierarchical network with adequate levels of quality and reliability. The introduction of SG contributes to providing digital intelligence to the power system network [56]. The benefits associated with these new concepts are: adequate management of the energy resources, reduction of the interruption rates, reduction of the pollution rates in the ecosystem, reduction in the number of interruptions due to problems in the quality of power and lower costs of operations and maintenance [1]. Consequently, one of the main benefits of SG is the intelligent and efficient design of hybrid communication networks, which take into account the congestion of the network, real-time transmission as suggested in [2; 47; 71] and the concern of reducing the emissions of greenhouse gases [69]. The fast growth of data requires researchers to pay attention to how to handle these data [72]. Therefore, three definitions have to be analyzed: volume, velocity and variety. Volume refers to the large amount of data to be processed; the speed refers to the latency of data transmission; and the variety refers to the different types of data that must be processed [59]. The consumers of energy resources are equipped with SMs that collect the data in real time. AMI receives all data and sends them to Meter Data Management Systems (MDMS) that controls the storage. MDMS is in charge of the analysis of data and provides the information in a useful way [73; 74]; in addition, the efficient management of wireless resources is essential to increase the life of the network [75]. AMI is not a technology, but rather a configured infrastructure that integrates a series of technologies to achieve their goals. AMI includes SMs, communication networks, MDMS and the tools to integrate the collected data of software application platforms and interfaces [16; 76]. Among the communication technologies used in this paper for extracting and transporting the information are WiFi, cellular and optical fiber. Optical fiber has dominated by being able to maintain communications over long distances, such as for metropolitan networks (see Figure 1). Additionally, it provides increased bandwidth, low transmission losses and greater tolerance to other cable access technology interference [77]. One of the disadvantages is that it requires a huge cost for a deep penetration of fiber. Therefore, the wireless access networks are a promising technology, since they provide the flexibility of low cost, increase the coverage and robustness and are easy to implement. A disadvantage is that the bandwidth capacity is limited severely [78]. Therefore, considering the advantages of each technology, it was proposed to build a hybrid network technology that includes wireless technology and optical fiber. The integration of renewable energy resources with small sources of storage leads to the concept of microgrids [74; 79]. The uncontrolled integration of microgrids affects the quality of the power, among which, the more important events are sag voltage signals induced by failure defects [80]. Therefore, with the insertion of DRES, the quality of voltage cannot be guaranteed when there is not a communications system to provide timely information of the state of the conventional network. To ensure the quality of voltage in the network, through the integration of microgrids, the voltage levels of the conventional network and the DRES must be resynchronized [81]. This resynchronization can be done by obtaining real-time information of the state of the network.