The effect of different attenuation models on the performance of routing in shallow-water networks

Several models can be used to determine the attenuation incurred by sound waves as they travel under water. A trade-off between accuracy and complexity is observed in this respect: the most accurate results are typically yielded by some form of numerical solution to the sound propagation equations, but at the price of high complexity; conversely, simple link budget equations are typically valid only as a first-order approximation, but are much simpler to evaluate. When such different models are applied to network simulations, both the accuracy and the complexity of the chosen model can have a big impact on the simulation time and on the significance of the outcomes. In this paper, we present a comparison among different models of increasing computational complexity for simulating the transmission loss of underwater acoustic channels, when applied to the simulation of multi-hop underwater acoustic networks. All models have been integrated in the DESERT Underwater framework, which is based on the ns2/MIRACLE network simulator. Our results show that the model and its parameters have in fact a big impact on network simulation results in different network topologies, which is consistent with the findings reported by some other papers that recently appeared in the open literature. Our results also show that in some instances simple propagation models provide a useful approximation if their parameters are properly chosen.