## 2 Related Work
CENTERA is not suitable for mission-critical wireless sensor networks because it is vulnerable to denial of service or on-off attacks and does not consider the priority of data. SQEER [11] is devised based on energy and trust modeling for enhancing the security of WSN and also to optimize the energy. The trust modeling utilizes a technique with a security mechanism for providing trust scores. A cluster-based trust routing protocol is designed in which the cluster head has been selected based on trust scores and QoS metrics to perform trust routing. In addition, trust scores, namely direct, indirect and overall trust scores, are evaluated for enhancing the security of communication. The final path algorithm has been allocated based on energy, path trust, and hop count to carry out the secure routing process. However, SQEER is limited in the MC-WSN environment because it transmits data by assigning it to a single path without considering the priority according to the importance of the mission of the tactical data. Moreover, it is not suitable because there are no considerations to satisfy the performance requirements of mission-critical data. TBSIOP [12] utilizes three distinct WSN attributes to compute a node's likelihood of being malicious. These attributes are in energy depletion, acknowledgment, and forwarding data packets, and these attributes are used for trust computation. TBSIOP deals with the selection of the best relay candidate among the potential forwarder candidates. The potential forwarder node will be chosen from a set of forwarder nodes based on trust values and probabilities of being selected from the forwarder list. TBSIOP proposes a method of selectively transmitting specific data without classifying mission-critical data. In this case, large-capacity data cannot be processed and the QoS factor of mission-critical data is not satisfied. ATRP [13] has been proposed that encompasses direct trust, indirect trust, and witness trust, considering multiple factors (resources and security) in its trustworthiness and using pairwise comparison. The proposed mechanism allows further evaluations of additional potential nodes at several hops, which helps to balance the energy consumption and prolong the network lifetime. The objective of the ATRP is to propose an efficient trust-based routing protocol for the selection of relay nodes in distributed WSNs based on multiple trust factors and multilevel trust evaluations using the Q-learning technique. The protocol employs multiple evaluations at multiple layers rather than single-hop evaluations. The consideration of multiple factors in the ATRP balances the load distribution in the network and provides a more accurate selection of the next forwarder. In the proposed approach, both successful and failed transmissions contribute to the calculation of the Q-values. The control mechanism unit in the ATRP is responsible for ensuring that the trust value is valid and reliable. There are three components in the control mechanism unit: number of interactions, decay time factor, and timeliness measurement. However, it is difficult to detect intelligent behaviors such as on-off attacks using this scheme, and it is hard to guarantee the QoS of mission-critical applications by proposing an energy-oriented reward function. In addition, ATRP is a protocol that is not suitable for operation in a mission-critical wireless sensor network environment because it does not sufficiently consider a method to satisfy the requirements of mission-critical data. Compared with such existing methods, trust-based intelligent routing is novel in terms of three aspects. First, a mission-oriented path allocation algorithm is proposed to meet the requirements of trustworthiness and QoS in MC-WSNs. Second, we suggest a Q-learning-based trust routing technology that detects clever attacks and ensures the reliability of mission-critical applications. Third, we propose a flexible weight for the energy and detection ratio in MC-WSNs.