## 1 Introduction
Critical power assets can be found along the three distinct segments of the electrical grid: Generation segment (where power plants and energy storage systems can be found), Transmission and Distribution (T&D) segment (where transformers, substations and power lines are installed) and Consumers segment (where end-users' premises are). However, the concern behind this approach is that designing the required WSN-based monitoring systems implies a profound knowledge of telecommunications and electronics involved, especially when dealing with an integral _ad-hoc_ solution. Furthermore, because of the particular nature of the power grid (mainly very harsh propagation conditions and the lack of appropriate inexhaustible power sources), systems intended to manage and control power assets have to fulfill specific requirements and be engineered with those requirements in mind. Therefore, the communication protocol stack and technologies used in WSNs for the Smart Grid must be revised and improved (when not specifically designed from scratch) to achieve the best results. Unfortunately, to the best of our knowledge, no integral _ad-hoc_ WSN solution has been proposed in the Smart Grid research field so far and only few approaches have intended to adapt well-known WSN technologies originally thought to operate in different fields [10; 11; 12; 13]. To address this shortcoming, and as the main contribution to this work, we propose a fully integral _ad-hoc_ control and sensing solution based on wireless sensing technologies (denoted as SENSED-SG) satisfying the major requirements of a Smart Grid monitoring application. This control and sensing solution is achieved by means of a novel protocol stack designed from scratch to appropriately exploit the benefits the SG and circumvent potential challenges. Special attention has been paid to the MAC and Network layer where the core of the communication system lies and its main settings tuned to attain good performance. In addition, our proposal has been evaluated and validated by means of theoretical analysis, computer simulation and extensive experimentation under controlled conditions: (i) a High Voltage AC/DC laboratory and (ii) the T&D segment of a power grid. As an additional contribution, our solution is compared to ZigBee, one of the most popular standards in WSNs in a Smart Grid environment. As far as we know, this is the first test-bed including multi-hop and cluster-tree topologies performed in a Smart Grid environment. The results reveal that our _ad-hoc_ solution, specifically designed for the Smart Grid area, is better suited than other solutions (like ZigBee) adapted to operate in this research field. The rest of this paper is structured as follows. Section 2 presents an up-to-date review of the particular requirements of a Smart Grid and the challenges the enabling technologies have to face. Section 3 introduces the related work found in the literature, summarizing their advantages and limitations. Section 4 describes our proposal as well as the mathematical analysis supporting the decisions made. The set of complex simulations conducted is reported in Section 5. The test-beds accomplished are explained in Section 6. Finally, Section 7 concludes and outlines future works.