# A Survey on Underwater Acoustic Sensor Network Routing Protocols  
[PERSON]  
1 Centro de Investigacion en Tecnologias Software y Sistemal Multimedia para la Socnibilidad (CITSEM), Campus Sur Universidad Politecnica de Madrid (UPM), 28031 Madrid, Spain; [EMAIL_ADDRESS] (J.-F.M. ); [EMAIL_ADDRESS] (J.M.M.C. ); [EMAIL_ADDRESS] (M.E.) 1 Centro de Investigacion en Tecnologias Software y Sistemal Multimedia para la Socnibilidad (CITSEM), Campus Sur Universidad Politecnica de Madrid (UPM), 28031 Madrid, Spain; [EMAIL_ADDRESS] (J.-F.M. ); [EMAIL_ADDRESS] (J.-F.M.C. ); [EMAIL_ADDRESS] (M.E.) 1 Centro de Investigacion en Tecnologias Software y Sistemal Multimedia para la Socnibilidad (CITSEM), Campus Sur Universidad Politecnica de Madrid (UPM), 28031 Madrid, Spain; [EMAIL_ADDRESS] (J.-F.M. ); [EMAIL_ADDRESS] (J.-F.M.C. ); [EMAIL_ADDRESS] (M.E.) 1 Centro de Investigacion en Tecnologias Software y Sistemal Multimedia para la Socnibilidad (CITSEM), Campus Sur Universidad Politecnica de Madrid (UPM), 28031 Madrid, Spain; [EMAIL_ADDRESS] (J.-F.M. ); [EMAIL_ADDRESS] (J.-F.M.C. ); juan.menes@upm.esunderwater environment is inefficient; thirdly, the special characteristics of underwater acoustic waves and channels limit the wide application of WSN technologies. In addition, underwater acoustic sensor networks are always deployed in the area where no arrangement in advance is possible, so the routing protocol should have the ability to build highly reliable and effective communication links without the help of pre-arranged devices. Moreover, in case the routing is broken during the data transmission, the routing protocol should able to repair or rebuild the routing in a timely way. The routing protocol must be robust and self-adaptive, which is very important for networks in harsh underwater environments. A large amount of research has been carried out on the design and application of underwater acoustic sensor networks. These works have investigated various aspects of UASNs, such as the routing protocol, the MAC protocol, the link layer protocol, the communication method, the localization algorithm, _etc._ In [3], the authors introduced the principles and characteristics of different routing protocols, and compared different aspects of the different routing protocols, such as the data copies, the transmission method, clustering _vs._ non-clustering, single/multiple sinks, the control packets, _etc._ In addition, the authors also classified the different routing protocols based on the network architecture, the data forwarding method, and the protocol operation. The work in [4] reviews the state-of-the-art of the underwater acoustic sensor network protocol design, including the research methods of underwater acoustic sensor network and the research challenges of the different layers (MAC layer, network layer, and transport layer). A similar review can be found in [5]. In this paper, the authors provided a comprehensive overview of the current research on underwater acoustic sensor networks and analyzed the state-of-the-art of research on the physical, MAC and network layers. Different from previous surveys, this paper focuses on the underwater acoustic sensor network routing protocol design. There are many kinds of communication protocols for underwater acoustic sensor networks, such as the MAC protocol, the topology control protocol, the link layer protocol, _etc._, but that research is out of the scope of this paper and can be found in other relevant research articles. In this paper, we only consider the routing protocols of UASNs. Different from the already existing UASN routing protocol surveys, we divide the routing protocols into two different kinds: the cross-layer design routing and the non-cross-layer design routing. We investigate the research articles published in recent years and briefly analyze the performance of these routing protocols.