# An Energy Efficient Routing Approach for Cloud-Assisted Green Industrial IoT Networks
## 3 Related Works
### RPL Optimization for Resource-Constrained Networks
Another enhancement of RPL to satisfy the challenges imposed by the Internet of multimedia things has been proposed in [43]. The authors proposed a new version of the RPL routing protocol named green-RPL to enable green communication for multimedia connected networks. Suchenergy-efficient routing solution reduces the network carbon footprint emissions by ensuring the QoS requirements of the multimedia application. In green-RPL, a node selects the preferred parent based on the set of network metrics, including battery consumption and energy source types. In terms of packet delivery, the green-RPL is better as compared to the default RPL OFs; on the other hand, green-RPL is less energy efficient than ETX. In [44], the authors have proposed a new energy consumption(EC) aware RPL-compliant OF using fuzzy logic named OF-EC. It combines multiple metrics such as ETX, hop count, and energy consumption to deal with the limitations of the single metric based RPL implementation. Although OF-EC combines node and link metric using membership function to select a parent node, it has neglected the resource utilization of a node, whilst it is one of the main concerns for resource-constrained networks. Similarly, the authors in [45] have introduced a new OF for efficient routing (ER) called OF-ER. To select the best parent, OF-ER uses the composite efficient routing metric. This metric takes into account multiple metrics, namely, ETX, queue utilization, delay, lifetime of node, and number of bottleneck nodes. However, it simply combines these metrics regardless of the isotonicity and monotonicity characteristics of the routing metrics. Although energy metrics have been widely used in RPL optimization, there have been limited studies on consideration of duty cycling for energy profiling during routing metric design. Moreover, most of the above RPL extensions adopt the residual energy of a node, either alone or in combination with other nodes or link metrics, so as to choose the best path. Besides, RPL enhancements have been made either for specific purposes, such as congestion control, mobility or designed to support various protocol functioning using techniques such as fuzzy logic, SDN, etc. Reliable data communication in order to ensure the ideal emergency monitoring system in different industrial operations is essential, in which the IIoT network may generate various types of data traffic such as time-critical and delay-tolerant. This backdrop motivates the authors to design the new composite routing metrics and OF to optimize RPL for the IEMS use case of IIoT. In order to extend the network life through reliable data delivery for the resource-constrained network, not only the resource availability is important but also the nodes' sleep and awake status is vital. Moreover, heavy computational systems like fuzzy logic, particle swarm optimization may degrade the performance of a resource-constrained network. Therefore, to distinguish the efficiency of the RAROF, we have considered fuzzy logic-based OF-EC and resource-aware OF-ER as benchmarks for the comparison.