## 4 Performance Evaluation
### Simulation Metrics  
Table 2 depicts simulation parameters used for performance evaluation of proposed DQN based MAC protocol in UWSN. Channel utilization (\(U\)) is measured to determine how effectively the communication channel is being utilized for transmitting and successfully receiving data in a network. It is defined as the fraction of the total available resources, such as time, bandwidth, and slots, that are used for successfully delivering data traffic to the sink node. The effectiveness of communication resource utilization is assessed through channel utilization (\(U\)). Low channel utilization is observed when the available resources are underused. This underuse may be caused by high protocol overhead, low data transmission rates, or scheduling mechanisms that fail to maximize resource utilization. Conversely, high channel utilization is indicated when the communication resources are employed effectively, with most of the time allocated to the successful transmission of data. However, excessively high utilization in contention-based protocols is associated with network congestion, increased collisions, and reduced overall efficiency. A balanced channel utilization is considered essential for ensuring efficient communication without overloading the network. The channel utilization U can be measured by using Equation (26) [37].  
\[U=\frac{D}{r_{uw}\times F\times S_{n}s\times T_{s}}. \tag{26}\]  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Network Parameters** & **Purpose** & **Value** \\ \hline \(N\) & Number of nodes in the network & 50 nodes \\ \hline Distance & Distance between a generating node and a sink node & 12.9 m \\ \hline Simulation Area & Area for node placement & 600 \(\times\) 600 m \\ \hline Traffic Rate & Rate of traffic generated by nodes & 0.05 to 0.4 packets/s \\ \hline
**Transmission Parameters** & & \\ \hline Data Packet Size & Size of the data packet & 1044 bits \\ \hline \(T_{dp}\) & Duration of a data packet transmission & 16.704 ms \\ \hline ACK Packet Size & Size of the acknowledgment packet & 20 bits \\ \hline \(T_{ap}\) & Duration of an acknowledgment packet transmission & 0.32 ms \\ \hline \(r_{uw}\) & Tx/Rx data rate & 62,500 bps \\ \hline Transmission Rate & Communication data rate & 13,900 bps \\ \hline \(v_{uw}\) & Propagation speed in the underwater medium & 1500 m/s \\ \hline \(\tau_{p}\) & Propagation delay & 8.6 ms \\ \hline \(T_{S}\) & Duration of guard time & 0.576 ms \\ \hline \(T_{s}\) & Slot duration in the TDMA schedule & 34.8 ms \\ \hline \hline \end{tabular}
\end{table}
Table 2: Simulation Parameters.  
Here, \(D\) represents the total number of data bits successfully received by the sink node, \(r_{\text{uw}}\) denotes the data rate in bits per second (bps), \(F\) is the total number of frames observed, \(S_{n}s\) is the number of slots within a frame, and \(T_{s}\) is the time duration of a single slot.  
We define the PDR as the ratio of data packets successfully received by the sink node to all the packets generated by the source node [43].  
\[\text{PDR}=\frac{P_{\text{received}}}{P_{\text{generated}}}. \tag{27}\]  
The efficiency of a network is measured by the throughput, which is calculated as the ratio of the total received packet bytes to the total transmission time during a simulation using Equation (27) [44].  
\[\text{Throughput}=\frac{\text{Received Packet\;Bytes}}{\text{Transmission\; Time}}. \tag{28}\]