## 5 Simulations
### Channel Performance in Presence of Surface and Bottom Reflections  
The algorithm will enable the creation of a network of nodes where the dimensions and parameters used to set up the network are the same as those specified before. However, in these simulations, fixed parameters will be considered: S = 35\(\%_{\infty}\), T = 29 \({}^{\circ}\)C, pH = 8, w = 1 m/s, f = 78 kHz, B = 30 kHz and c = 1500 m/s (speed of sound propagation). The nodes are distributed random in total depth [0, 200]. The nodes that are placed below 1/3 of the values of [0, 200] (the highest depth) are selected as sources nodes (Figure 3). The relay node is selected by Equation (23) by being a node inside the depth's range, (Figure 3). The destination is selected by Equation (23) by being a node inside the depth's range, (Figure 3). The node that is almost in the surface of the sea, with the least depth. There will be an evaluation of some basic metrics like network lifetime, number of packets transmitted, acoustic channel capacity in (kbps) and total time delay in (ms). The first two metrics are evaluated in the same way as before, while the other two metrics i.e., capacitance and delay are averaged for each acoustic channel created for Tx/Rx communication, since in this case the number of reflections will vary according to [12], caused to the fact that the propagation path into shallow areas can include from tens to hundreds of reflections. The multipath phenomenon as well as the effects that this phenomenon brings to the acoustic channel capacity or network lifetime, will be simulated by considering a number of reflections where the first reflection occurs on the surface (each graph and conclusion presented with respect to the mentioned metrics is an averaged result 100 simulations performed). Evaluated metrics will also be compared in cases where oceanic bottom material changes, like volcanic rocks, limestone, sand, gravel whose geo-acoustic properties are shown in Table 1.  
The first simulation was performed regarding the effect of the number of reflections (multipath propagation) for an oceanic environment whose bottom material is made of bas  
Figure 9: Lifetime versus temperature. that the velocity of sound propagation in this environment is 5250 m/s, much higher than 1500 m/s which is the velocity of sound propagation in water. According to the simulation presented in Table 4, the channel capacity available for acoustic communication decreases as a result of the multipath effect (propagation according to many paths due to surface and bottom reflections). As a result, the SNR ratio in the receiver would decrease, a phenomenon which, according to [PERSON] [11], would be translated into capacity reduction. The effect of multipath has a stronger impact on capacity than environmental effects such as changes in temperature or salinity (it greatly reduces the capacity of acoustic communications) and that is why the multipath effect is one of the main problems of underwater environment. Apart from the simulation carried out, the performance of the estimation metrics under the conditions of various materials at the bottom of oceans is of great interest. Recall that for these materials (basalt, limestone, gravel and sand), the sound propagation velocity ratios in those versus velocity of sound propagation in water (1500 m/s) are 3.5, 2, 1.2, 1.1 and material density ratios against water density (1000 kg/m\({}^{3}\)) are 2.7, 2.4, 2, 1.9. Tables 5 and 6 present a comparison between the performance of acoustic communication capacity and lifetime for the four materials. The materials basalt and limestone referred to others (Table 1) are less porous, and this results in smaller losses. Both capacity and lifetime decrease with increasing number of reflections. However, the acoustic communication capacity where the bottom area is basalt, would be higher than in an area of limestone bottom material.