## 4 Performance Analysis
### Results and Discussion  
In this section, the results obtained from the single channel protocols with interference are compared with the multichannel protocol with the same interference rate of 15% (low), 35% (moderate) and 55% (high) in UWSNs. During simulation studies, it is noticed that the packets delivery ratio is found high in all routing protocols when the interference rate level is 15%. The interference does not heavily affect the transmissions in a single channel protocol at the beginning as the interference is not frequent enough, showing the average 87%, 90%, 92% reception rates in LRP, QERP and MERP in the first 30 s as shown in Figure 6. This is because the nodes in these routing schemes have enough time to recover from the interference through retransmissions. However, the packets delivery ratio decreases rapidly over time when the interference level is linearly increasing from 15% to 55%. From low to high, the packet loss increases over time and always goes up until 16%, 14% and 11% in MERP, QERP and LRP routing protocols. This rate is found to be extremely low around 1% in QoSRP nearly throughout the simulation period, compared to all other routing protocols in UWSNs. However, the overall packets delivery ratio is recorded high around 89% in MERP compared to 86% and 84% in the QERP and LRP routing protocols in UWSNs. During simulations, it is observed that due to the presence of interference, the single-channel protocol shows deteriorate reception rate in UWSNs. The reason for these losses is because the network is being congested with retransmission packets. The congestion management profile of each routing protocol is shown in Figure 7. It indicates that the congestion management efficiency of QERP is higher around 90% compared to the MERP and LRP routing protocols. On the other hand, the congestion management profile of MERP and LRP are overlapping each other and is around 83% and 82%, respectively. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value (s)** \\ \hline Channel & Underwater channel \\ Network topology & Random \\ Deployment area & \(1000\times 1000\times 500\) m\({}^{3}\) \\ Initial node energy & \(100\) J \\ Initial sink energy & \(100\) kJ \\ Number of nodes & \(250\) \\ Cost of high transmission & \(1.5\) W \\ Cost of low transmission & \(1\) W \\ Cost of reception & \(0.75\) W \\ Idle power & \(0.01\) W \\ Data aggregation power & \(0.35\) W \\ Communication range of ASN & \(150\) m \\ Acoustic transmission range of sink & \(200\) m \\ Spreading values & \(1.5\) \\ Frequency & \(30.5\) kHz \\ Number of Channels & \(11\) (\(30.511\), \(30.518\), \(30.525\), \(30.532\), \(30.539\), \(30.546\), \(30.560\), \\  & \(30.553\), \(30.567\), \(30.574\), \(30.581\)) kHz \\ Maximum Bandwidth & \(30\) kbps \\ Packet size & \(50\) bytes \\ Control packet size & \(5\) bytes \\ Packet generation rate & \(0.01\)\(\sim 0.1\) packets/s \\ Memory size & \(10\) MB \\ Maximum sink and ASN & \(1\) km \\ Antenna & Omni-directional \\ Simulation time per epoch & \(150\) s \\ Number of runs & \(53\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Values of parameters used in QoSRP. In these single-channel protocols, the node does not have enough time to recover from the high interference to retransmit and drops most of the packets. There are more packets being dropped over time and the node stops receiving packets as it does not have enough buffer space to store the incoming packet and the channel becomes congested. However, the MERP protocol data delivery performance improves as the interference rate increases since it has more time to recover compared to the QERP and LRP routing protocols. On the contrary, the overall packets delivery ratio is recorded high at around 99% in QoSRP in UWSNs. In QoSRP, the number of packets received at the sink is observed around 88% when the vacant channel's record is found to be around 5 at each ASN in UWSNs. Figure 6: Packets delivery ratio vs. number of channels. Figure 7: Congestion management vs. number of rounds.