Modeling Underwater Communication for Autonomous Underwater Vehicles in OMNeT++ Peter Danielis, Mostafa Assem Mohamed Ali, Helge Parzyjegla Institute of Computer Science, University of Rostock Rostock, Germany peter.danielis@uni-rostock.de Abstract—Recently, cooperative Autonomous Underwater Ve- hicles (AUVs) have been deployed in application areas such as surveillance and protection of marine infrastructures for inspec- tion and monitoring purposes. These cooperative methodologies require wireless transmission of data between the different AUVs operating in the underwater environment. Communication over ranges exceeding 100 meters exclusively relies on underwa- ter acoustic communication. However, the propagating acoustic waves suffer from several challenges due to the presence of path loss, multi-path propagation, the slow and variant propagation speed, background noise, and Doppler distortion. Due to the difficulties of real experiments, the modeling and simulation of underwater acoustic communication play an essential role in studying and developing these systems. We provide a modular simulation model for acoustic underwater communication of AUVs implemented in the network simulator OMNeT++ using the INET framework. More specifically, we extend several INET modules in such a way as to reflect the characteristics of under- water communication. We study and analyze the dependence of the message quality on different properties such as those mentioned above. The model focuses on the transmission medium and physical layer of the communication channel. I. I NTRODUCTION After the World War II, military ammunition was disposed of in the Baltic Sea. The areas with unexploded ordnance (UXO) are roughly known, e.g., the Kolberger Heide northeast of Kiel in Germany. However, the exact location and number of the ammunition as well as their condition are unknown, which makes these areas very dangerous. One feasible way to locate thix UXO in order to render it harmless and dispose of it properly is to use several Autonomous Underwater Vehicles (AUVs) such as the Atlas Seacat. These AUVs are equipped with a survey head comprising multiple sensors and an acous- tic modem for communication [1]. Acoustic communication is considered to be the preferred technique of communication under water for communication ranges over 100 meters as the acoustic waves suffer relatively less attenuation than radio- frequency signals. The AUVs have to communicate with each other in order to collaboratively complete their tasks fast and also in an energy-efficient way since they are subject to restric- tions on the energy available to them. Messages sent to each other can, e.g., contain data about the area of investigation, location data, or power consumption data. Acoustic under- water communication is a complex process since it suffers, among other things, from fading, multipath propagation, the slow speed of acoustic waves underwater, background noise, attenuation, and motion-induced Doppler effect. In this paper, we present a simulation model for underwater communication of AUVs implemented in the simulator Objective Modular Network Testbed in C++ (OMNeT++) using the framework Internet networking (INET). We extend several INET modules to reflect the characteristics of underwater communication. We use our model to study the communication quality underwater and to test different scenarios. The remainder of this paper is organized as follows: In Section II, we compare our approach with the related work. We introduce the simulation model design and its OMNeT++ implementation in Section III. In Section IV, we outline the simulation setup and we present results from our OMNeT++ simulations. Finally, we conclude the paper in Section V, and present directions for future work. II. RELATED WORK This chapter gives an understanding to and summarizes a number of related works for acoustic underwater communica- tion models and simulators, which cover different aspects of the communication channel. In the work of Xie et al., the authors developed a simulator based on NS-2 for underwater sensor networks, Aqua-Sim [2]. The model simulated the attenuation of the acoustic signals and the packet collisions that happen in the network. They presented an attenuation model, which depends on commu- nication distance, frequency, and spreading factor. Due of the challenging conditions in underwater communication, they developed a collision model for every node. Moreover, they implemented four MAC protocols and conducted different case studies to compare these MAC and routing protocols. Barbeau et al. have modeled the physical, link, network layers of the underwater acoustic communication as well as the mobility of the nodes due to the influence of the communication distance on the communication channel [3]. The model implemented the attenuation, which is frequency and communication distance-dependent according to the Throp model [4]. The mobility of the nodes presented a variable communication distance, which was used in the attenuation calculations. They integrated the physical layer model, which is implemented in MATLAB, into OMNeT++. In the work of Geng and Zielinski, the authors addressed the limitation of the Rayleigh fading model, which is used in terrestrial communication and commonly used in underwater acoustic