## 1 Introduction
They chose Relevant Link Metric Types (RLMTs) for each application (traffic type), assigned different weights to each of them, and used a pruning technique to reduce the number of considered paths to a given destination. The best link to send each traffic was then calculated by means of an AHP (Analytical Hierarchy Process) algorithm. The proposal was evaluated by means of ns-2 simulations, over a usual network environment consisting of a grid of smart meters transmitting (receiving) information to (from) a data concentrator and taking into account four basic CBR traffic types. Moreover, the topology was modified by increasing the number of smart meters (from 25 to 64) and changing the data concentrator position. The network performance was measured in terms of dropped packets, packet delivery ratio and average delay, showing a better behavior when compared to a basic OLSR implementation. The same authors previously presented in [13] a performance evaluation and comparison of the OLSR and HWMP (IEEE 802.11s) routing protocols, together with a classification of the main AMI application traffic. A multi-gate communication network, based on IEEE 802.11s, was proposed in [7] for smart grids. The authors took into account the possibility of having more than one node acting as a gateway, together with a real-time traffic scheduling and a multi-channel-aided routing protocol. Besides, the authors proposed a heuristic backpressure scheme, where every node evaluated the state of its neighbors before selecting one of them as the best next hop, which implies that some information (the backpressure metric) must be periodically exchanged between nodes. Otherwise, to avoid loop problems, a hop-count limit was imposed on the data packets. Besides, in order to reduce the effect of co-channel interference, a multi-channel protocol was also introduced. To evaluate the proposals, three simulation scenarios were taken into account: (a) three separated sub-networks where every one had its own gateway, (b) a multi-gateway network where the three previous networks shared their three gateways and where the nodes were uniformly distributed, and (c) the previous configuration, but with an asymmetrical distribution of the nodes. The results showed the better behavior offered by the proposed backpressure scheme in terms of overall throughput, average end-to-end delay, and adaptation to malfunctioning nodes. On the other hand, the benefits of the multi-channel protocol were also clearly shown. A cross-layer mechanism that combines information from the physical, MAC, and network layers was presented in [14]. Based on that mechanism, the authors defined a new routing metric (Expected Path Throughput (EPT)) and a distributed routing protocol, which was evaluated with the help of the ns-2 simulator. The results showed the good behavior of the proposal when compared with other classical metrics and protocols. In [15], the authors proposed the HWMP-NQ protocol, a modification of HWMP to ensure the Needed Quality of Service (QoS) of several smart grid traffic types. To this end, the airtime link metric was modified by considering the packet size and the transmission rate. However, the needed number of channel measurement could be excessively increased. To avoid this, a frame error rate computing algorithm based on a single measurement was also proposed. Besides, the benefits provided by a multi-gateway backup routing scheme were also analyzed. Moreover, to reduce the routing overhead in case of link failures, a modification of the path error mechanism was introduced. To evaluate the benefits of their proposals, the authors built classical NAN grid topologies with the help of the ns-3 simulator and ran multiple simulations to measure the average throughput, packet delivery ratio, end-to-end delay, and routing control information overhead. The results showed the benefits of the multi-gate routing scheme presented in [7] and the HWMP-NQ protocol, in front of the classical HWMP implementation, for different NAN grid sizes (from 9-64 smart meters).