## 1 Introduction
Towards enabling fault-tolerant routing, the first step is to establish the multi-node/link disjoint routes, comparing these with the previous route as well as all other alternative routes. In this mechanism, the failure in the previous route due to the breakdown of any or all nodes/links has no impact on the alternative routes; this since, in the energy-harvesting environment, the time-varying, unstable, and random nature of harvested energy may compel the nodes to fail. Furthermore, due to this random nature of harvested energy, the nodes' lifecycle frequently switches between alive and dead, which results in dynamic changes in the quality of the routing. The designing of effective fault-tolerant routing in EH-WSN is a hard nut to track since it constitutes the NP-complete problem. For providing fault tolerant routing, a few research articles recently were published; e.g., [PERSON] et al. [14] proposed a fault-tolerant routing scheme utilizing clustering for WSN; [PERSON] et al. [15] presented a multipath routing model with features such as increased reliability, minimum latency, and cost-effectiveness. In the proposed model, there exists a backup node in each route. The backup node is responsible for storing the data from the parent node for maintaining the continuity in case of failure. [PERSON] et al. [16] also proposed an energy-efficient routing scheme based on a greedy strategy. In the proposed scheme, an energy evaluation model is constructed first for identifying the energy state of the node. Further, a range judgment framework was designed, and these two schemes were combined for designing a reception state adjustment scheme. Researchers are using various techniques based on approximations, heuristics, etc., for providing the appropriate solution for the relay node optimization problem, as well as to solve the NP-complete problem of fault-tolerant routing in EH-WSN. Metaheuristicsare used currently for providing the solution to these non-deterministic polynomial time (NP)-hard and NP-complete optimization problems, respectively. The major reason for using metaheuristics for solving these problems is that these frameworks are efficient in handling NP-hard as well as NP-complete optimization problems, having non-linear characteristics. As compared with heuristic algorithms, metaheuristic algorithms have added advantages since metaheuristic algorithms are intelligent enough and also have adaptability features; in turn, heuristic algorithms are mainly problem dependent. The two main pillars of stochastic algorithms are a deterministic component and a random component. Further, the local optimum can be found by a deterministic component, on the other hand, with the help of a random component; metaheuristic algorithms also can adopt various forms by considering random walk and random sampling. In this research article, a novel framework is proposed, namely, a framework enabling fault-tolerant and reliable green communication in next-generation wireless systems (FRGNWS), considering a single-tiered EH-WSN with constrained RNs deployment. The proposed novel framework consists of two phases. In the first phase of the proposed novel framework, maximum node-disjoint routes from all SNs to BS using minimum RNs are explored based on a hybrid adapted grey wolf sine cosine optimizer (HA-GWSCO) framework, the HA-GWSCO framework also discovers k-node-disjoint routes from each SN to BS with k \(\geq\) 2, which enhances the fault tolerance capability in EH-WSN. In the second phase of the proposed novel framework, out of the k-node-disjoint routes from each SN to BS with k \(\geq\) 2, the best appropriate reliable route is selected for routing, which enhances the reliability in routing for EH-WSN based on the hybrid adapted grey wolf whale optimizer (HA-GWWO). The salient contributions of this proposed novel research are listed below in a point-wise fashion. 1.