## 3 Related Work  
Many papers have looked into the requirements of a Smart Grid as the main way to understand the big picture [14, 15, 27], on the other hand many others have kept the focus on the challenges diverse technologies have to face in order to implement a Smart Grid [16, 31]. However, as far as we know, there is no single work that unifies these two aspects--requirements of a Smart Grid and what challenges the enabling technologies have to tackle to achieve them--with the aim of setting the starting point for a Smart Grid suitable control and sensing solution.  
Works in [3, 32, 33] have studied the performance of some technologies/protocols and their behavior in \"simulated\" smart-grid environments obtaining good results. Nevertheless, we believe that individual technologies that are interconnected to form a bigger system cannot be analyzed independently since doing so will overlook the non-trivial interaction between them. For instance, in [34] a new secure routing protocol including quality of service support for Smart Grids is presented and analyzed. Although several simulations are shown and their outcomes discussed, the authors omit the effect of an underlying MAC (Medium Access Control) layer that may severely deteriorate the results (e.g., it is notorious that many MAC protocols do not appropriately deal with certain types of data traffic like broadcasts or multicast packets). In this regard, our analyses and test-beds are aimed at providing results of different performance metrics considering every possible interaction between protocols--as will be reflected in Sections 6 and 7. In short, a complex system cannot be analyzed as the sum of its composing elements.  
In [35], a performance evaluation of a ZigBee-based approach for different Smart Grid environments is carried out by means of ns-2 simulations. However, the paper depicts an unrealistic scenario for a Smart Grid since every sensor node has a direct connection (no intermediate hops) with its sink; thus, leaving out the critical impact on the performance of a routing algorithm. Regarding ZigBee standard, many works have studied the suitability of this solution for the Smart Grid field [9,10,36], but ignored in which segment of the power distribution grid the standard would be deployed. This is an important fact in multi-hop networks, since ZigBee requires the presence of router devices for the network to be set up, and these devices entail a higher consumption of energy, as will be explained in the following sections. This situation forces devices to be connected to a power source to ensure a long lifespan; thus, clearly restricting the applicability of such networks to residential zones where nodes can be more easily powered. Therefore, our work pays particular attention to the segment of Transmission and Distribution since, in our opinion, this is the segment where current solutions are less effective.  
Other potential technologies like PLC (Power Line Communications) and Wi-MAX have been studied in [15,27,31] and their advantages outlined. However, it must be understood that a network based on PLC would have two major drawbacks: firstly, if there exists a breakdown in the actual electricity line, communications would be impossible. Secondly, the scalability of the solution is quite restricted due to the short bandwidth that this technology provides [37]. On the other hand Wi-MAX is only suitable for gateways or sink nodes (connected to power sources) because of its very high power consumption.