# A _uv_-Cellular Network: Design, Implementation and Experiments
## 2 Related Work  
Research on hydroacoustic networks started in the 1990s. The concept of Autonomous Ocean Sampling Network (AOSN) [10] was proposed in 1993. AOSN is an approach toward four-dimensional ocean sampling in the coastal frontal zone. It is done with several AUVs as well as with distributed acoustic and point sensors. And the AOSN-II experiment was conducted in 2003 [11]. During this a month-long experiment, up to 10 or more AUVs were deployed simultaneously to complete the depth, temperature, salinity, particulates, chlorophyll and light intensity data collection. The Seaweb program was proposed and developed in 2000s [12; 13; 14; 15]. In the trials conducted in 2001, a submarine maneuvered around a 14-node Seaweb network accompanied by two RACOM buoys. And a chain-like network experiment conducted in 2004 with 40 fixed nodes. Persistent Littoral Undersea Surveillance Network (PLUSNet) [16] has been established by the US navy since 2005. It is a semi-autonomous controlled network of fixed bottom and mobile sensors for keeping a constant eye on littoral zones. Its prototype system was delivered in 2015 and includes five underwater gliders and six REMUS AUVs. The Acoustic Communication network for Monitoring of Environment in coastal areas (ACMETnet) [17] project, supported by the European Union, is a long-term hydroacoustic communication network for real-time observation of the coastal environment. ACMEnet uses the MFSK/TDMA master-slave network protocol. Three fixed nodes form the minimum ACMENet system. Smart and Networking Underwater Robots in Cooperation Meshes (SWARMs) [18] project is sponsored by Horizon 2020. The main goal of this project is to reduce the operational cost and increase the safety of tasks assigned to unmanned underwater vehicles (AUVs/ROVs) in the operations.The project validated networked communication between the land-based control center and multiple underwater robots in multiple trials. All the above mentioned works have made significant progress in hydroacoustic networks, but they still need further research and validation in terms of network scale, heterogeneous node networking, and networking flexibility. In recent years, significant advances have been made in the development of UANs. As the demands increasing in communication between various remote instruments within a network environment, a lot of efforts have been made to establish large-scale UWSNs for different scenarios. A full duplex UAN [19] was proposed in 2022. In this study, they proposed a spatial reuse scheduling algorithm that exploits full duplex communication. In [20],the AUVs' synchronization is used to achieve multi-hop communication for delivering data to a sink over large-scale coverage areas. However, the synchronization mechanism is a greater challenge for the underwater networks which is energy-constrained. Ref. [21] also introduce a data collection method especially for the AUV aided UWSNs. It helps to solve two critical problems, the energy constraint of underwater devices and large demand for data collection. In [22], a probabilistic Space Division Multiple Access (SDMA) method for short/medium distances (less than 2 km) is presented. This method is useful for achieving a reliable coordination among the AUVs in the acoustic communication channel. DARP [23] is a depth adaptive routing protocol which considering the speed of acoustic signal varies with water depth. But its application scenario is more oriented towards 3D underwater networks consisting of fixed nodes. In [24], two approaches for scheduling large-scale underwater networks are proposed. The centralized scheduling approach yields the most efficient schedules and the clustered-based approach provides significant benefits in terms of communication and computation. In addition, a lot of efforts have been made in the field of localization schemes for large-scale UWSNs [25; 26]. There is also a lot of work focused on the testbeds of the UANs in a real environment.