## 2 Related Work
Although the authors focused on the analysis of DES frameworks, they proposed a list of characteristics that a good network simulator must have. The list comprised simulation-specific metrics such as robustness, scalability, and accuracy, and others related to visualization and support. From a testing and validation viewpoint, DES is usually subject to the quality of the used simplified models. Therefore, their robustness and accuracy are normally below other approaches such as _software-in-loop_ and hardware-in-loop schemes. The aforementioned schemes and frameworks were focused on providing a higher abstraction level for protocol implementation. However, they did not offer the possibility of evaluating already-existing protocol stacks. Unlike UnetStack, MULE, HTOSSIM, or Click, this work's network simulation proposal treats the protocol stack as a black box, interacting at byte level. Table 1 shows a comparison between the presented frameworks. Routing algorithms are a fundamental part of WSN since they greatly define the network's lifespan. The research community has traditionally put a significant amount of effort on this topic and the proposals are generally evaluated using network simulation frameworks [23; 24; 25]. This approach is interesting when both MAC and PHY layers are well-known and are properly modeled [26]. UWSN (and WSN in general) research has relied on this assumption. However, in most cases new MAC protocols are proposed, and performance estimation of actually-deployed nodes using event-based simulation is unfeasible. [PERSON] et al. developed an UWSN simulation environment based on NS-3 for UAC [27] in an attempt to model real hardware. The framework included not only PHY and MAC modeling, but also weather conditions since they severely affect the communications performance of ultrasound-based underwater links. Furthermore, energy-harvesting capabilities on the deployed nodes were also simulated. The authors included a detailed energy consumption framework considering different events such as wake-up, reception, idle state, and transmission, allowing a fine analysis of the network. Nonetheless, the authors only tested a star-like topology and source code emulation was not supported. STANAG 5066 has been widely used in military maritime communications. In theory, this stack is capable of supporting common network-level protocols such as IP. [PERSON] et al. analyzed the feasibility of using STANAG 5066 to support e-mail applications [28]. The authors compared the performance of IP-over-HF and proxy agents such as HMTP or CFTP. The experimental results suggested that proxy agents provide higher throughput due to their robustness against packet delay, which is an important issue in HF communications due to the reduced bandwidths and the harsh \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Framework** & **Scalability** & **Synchronization** & **GUI** & **Source Emulation** \\ \hline SensorSim & No & No & Yes & No \\ MULE & Yes & Yes & No & Yes \\ EmStar & No & Yes & Yes & No \\ Semu & Yes & Yes & Yes & No \\ H-TOSSIM & Yes & Yes & Yes & Yes \\ Click & Yes & Yes & No & Yes \\ UnetStack & Yes & Yes & No & Yes \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison between different Wireless Sensor Network (WSN) frameworks [15; 18; 22]. channel. In their following work, [PERSON] and [PERSON] simulated how the ARQ parameters of STANAG 5066 may affect performance [29]. The authors observed that the optimum frame size depends on the channel's average Signal-to-Noise Ratio (SNR). Taking into account the variability of the HF channel, the authors concluded that an adaptive algorithm should improve the overall performance. [PERSON] studied the impact of using the high data rate HF waveforms of STANAG 4539 on STANAG 5066's performance [30]. This work was motivated by the need to improve the HF communications' throughput. [PERSON] carried out several experiments in which interleaver, message, and packet sizes were varied, providing some recommendations as key outcomes.