## 4 Results and Discussion
### Characterization of S-RLNC for UWSNs  
Upon assessing the effectiveness of the proposed SRLNC scheme for efficient data transmission and finding it optimal, it was applied for data transmission over UWSN. To examine the effectiveness of the proposed UWSN routing protocol, we considered [53; 54] as a reference routing protocol. The overall algorithm including channel model and systematic RLNC based UWSN routing protocol has been developed using the MATLAB 2015a simulation platform. To perform the simulation, a total of 800 nodes were distributed across UWSN in 3D network environment (Figure 1). Here, the acoustic signal's propagation speed was taken as 1500 m/s. Each sensor node has the radio range of 250 m, and the initial energy was 100 J per nodes. Further, the rate of consumption was 60 uJ/bit. A number of packets of 64 kB size were generated by the source node. Now, considering SRLNC implementation for UWSN simulation, the number of packet combinations per generation is fixed at 10, with Galois Field size 8. As presented in Figure 8, our proposed SRLNC based routing protocol outperforms GPNC based UWSN routing. However, the effect of link loss on the packet delivery ratio (PDR) can be easily observed. In Figure 8, the average PDR of the GPNC protocol is 82.8%, while our proposed SRLNC based routing exhibits 94.85% PDR. SRLNC exhibited 12.5% higher PDR than GPNC based UWSN routing. Figure 9 depicts the effect of the number of nodes on PDR. Results reveal that with an increase in the number of nodes, PDR increases gradually. GPNC has exhibited on average 81.9% of the PDR, while SRLNC ensures 90.28% PDR, which is almost 8.4% higher than GPNC. The similar result can be observed from Figure 10, where our proposed SRLNC scheme exhibits approximately 4.8% higher throughput than GPNC. In UWSN's delay is one of the key factors required to be optimal [55].  
Figure 7: Effect of the number of redundant packets on S-RLNC throughput.  
Figure 11 presents the results obtained for the effect of the number of nodes on the average delay. The proposed SRLNC based UWSN routing exhibits 12.53% lower delay than the GPNC protocol. This is because of increased throughput, reduced data drop and, no doubt, enhanced FEC mechanism. Observing the above discussed results and their significances where the proposed routing scheme provides higher data delivery rate, throughput and minimal delay, it can be understood that with such accomplished performance, the probability of retransmission should be minimal and so should the energy exhaustion. To confirm this, Figure 12 justifies that the proposed routing scheme results in lower energy consumption than the GPNC based routing protocol. Here, SRLNC consumes approximate 24.3% less energy than the GPNC based routing approach [56; 57; 58].  
Figure 8: Effect of link loss rate on packet delivery ratio.  
Figure 10: Effect of number of nodes on overall throughput.  
Figure 9: Effect of number of nodes on packet delivery ratio.  
Thus, observing overall results and their inter-relations with the proposed channel model, systematic RLNC and its implementation with the UWSN routing scheme affirm that the proposed approach can be vital to ensure an efficient communication system for UWSNs.