## 3 System Model  
A WSN is represented as a graph \(G(N,C)\), where \(N=\{n_{1},n_{2},n_{3},\ldots,n_{t}\}\) signifies a collection of nodes and '\(t\)' denotes a set of connections between nodes \(n_{i}\) and \(n_{j}\). Consider that nodes lie within the coverage area (A) of a WSN. Every connection will be based on the delay that occurs while transmitting data and also based on the distance between '\(n_{i}\)' and '\(n_{j}\)'. Assume 'S' as the transmitting node that forwards data to the intended destination (D) through intermediary nodes. Our congestion-free, trust-aware, secure routing protocol ensures data security based on trust and reduces network congestion through priority-based data delivery. In the proposed scheme, malicious nodes are circumvented so as to ensure trust. They are not involved in communication, thus reducing the amount of traffic. Further traffic load is taken into consideration when determining the cost function. Furthermore, traffic is prioritized to avoid delay. All these factors contribute to security and reduction in congestion in the network. Figure 1 shows the communication of data in a typical WSN.  
Parameters such as trust, waiting time, energy, and distance are taken into consideration. These parameters, referred to as weights, are used in the determination of FF, which aids in the selection of optimal routes based on application demands. The classification of traffic enables the data traffic to be prioritized depending on the significance of application needs. FF is based on hybrid KHM and the GSA algorithm, as discussed in Section 4, and is used for optimal route selection based on node quality and data traffic. The following sections describe the method for determining fitness parameters. Further, the notations used are listed in Table 1.  
\begin{table}
\begin{tabular}{c l} \hline \hline
**Notation** & **Definition** \\ \hline RSSI & Received signal strength indicator \\ \hline \(Dist_{s,i}\) & Signal system strength between source node S and current node i \\ \hline \(G_{i}\) & \(i^{th}\) node in the graph \\ \hline \(Trust_{DT}(i)\) & The degree of direct trust which is present inside a node at time \(i\) \\ \hline \(Trust_{IDT}(i)\) & The degree of direct trust which is present inside adjacent nodes at time \(i\) \\ \hline \(\omega,\gamma\) & Fitness factors \\ \hline \(N_{d}\) & Number of neighbouring nodes \\ \hline \(\tau\) & Fitness factor which is utilized to stability of the measurement in the prevailing and past iterations that are stated between the range \(0<\tau<1\) \\ \hline \(N_{Ce}\) & Energy consumption of sensor node \\ \hline \(N_{TXe}\) and \(N_{RXe}\). & Energy Spent during transmission and Reception \\ \hline \(N_{LXe}\) and \(N_{SXe}\). & Energy Spent during idle and sleep mode \\ \hline \(N_{Re}\) & Residual energy present in a node \\ \hline \(N_{le}\) & Initial energy of a node \\ \hline \(T_{i}(k)\) & Buffer length of \(k\)th node \\ \hline congTh(min) & Minimum threshold for congestion \\ \hline congTh(Max) & Maximum threshold for congestion \\ \hline \(dist_{1}\) & The distance between current source node and potential next node \\ \hline \(dist_{2}\) & The distance between potential next node to sink \\ \hline \(\alpha,\beta\) & Adjustment parameters \\ \hline \(T_{wmax}\) & Pre-defined maximum waiting time \\ \hline \(Avg(S_{i}^{k})\) and \(S_{n}\) & Average speed of the nearest nodes inside transmission range and the speed of the node \\ \hline \(\delta,\epsilon,\psi,\gamma,\upsilon\) and \(\tau\) & Adjustment parameters lie between 0 to 1 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Definition of notations.  
Figure 1: Data communication in WSN.