A Topology Control with Energy Balance in Underwater Wireless Sensor Networks for IoT-Based Application  
[PERSON]  
1 Faculty of Mechanical Engineering & Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China; [EMAIL_ADDRESS] (X.P. ); [EMAIL_ADDRESS] (W.L. )1 Faculty of Mechanical Engineering & Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China; [EMAIL_ADDRESS] (X.P. ); [EMAIL_ADDRESS] (W.L. )1 Faculty of Mechanical Engineering & Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China; [EMAIL_ADDRESS] (X.  
data to perform on-line real-time monitoring tasks. Specially, each node can be controlled to float up or down by its buoy and pumping to freely anchor a certain region to form a two-dimensional or three-dimensional network. The collected information is forwarded on the acoustic modem after data processing and storage. UWSN can be applied to marine exploration, aquaculture, water quality monitoring and pollution prevention [3; 4]. Since radio is seriously attenuated in water, acoustic communication is almost the only effective way for underwater wireless transmission. Nevertheless, compared with the traditional radio, underwater acoustic communication is greatly affected by poor conditions, such as absorption, scattering, multipath interference and Doppler effect. Usually, the speed of acoustic transmission is 1500 m/s underwater [3] while it spreads almost 3\(\times\)10\({}^{8}\) m/s in the air by the radio. Obviously, there are five orders of magnitude difference between underwater and air communication. Due to the low rate propagation speed, the transmission delay of the underwater acoustic channel is always much higher in UWSN than the terrestrial wireless sensor networks (TWSN) [5]. This not only results in less throughput and lower communication efficiency, but also leads to increasing the probability of communication collision among the nodes. On the other hand, the reliability of data transmission is reduced by the multipath effect of signal propagation. It needs to resend data multiple times, which means it costs several time more energy consumption. In addition, a part of nodes may be unavailable to work during the network running, e.g., sudden failure or energy exhaustion, which cannot guarantee the connectivity and coverage of the entire network. To solve above issues, an effective topology control scheme for UWSN is particularly important. Generally, topology control which mainly consists of topology construction and topology maintenance is one of the efficient solutions for saving energy and prolonging lifetime [6]. Thus, the main purpose of topology control is to close the idle nodes or cut off the unnecessary links. Basically, energy-efficiency is the most important target for UWSN to reach. This is all because the energy is dissipated much more on underwater acoustic or hybrid communication. Furthermore, the quality of service (QoS) such as packets throughput should be guaranteed during the communication procedure, while preserving the connectivity and coverage of the entire network. This paper focuses on energy-efficient-based topology control for UWSN with clustering strategy using tree approach. We propose TCEB, a topology control algorithm with energy balance, which addresses the problem of how to find a reasonably reduced topology and the packets forwarding route. In TCEB, the whole process is mainly divided into three aspects: the non-cooperative-game-based cluster-head selection, the intra-cluster topology construction and the inter-cluster topology construction. Each part of work is performed to ensure energy-efficiency and make the whole underwater network load balance. Consequently, with energy conservation as the target, the main contributions of this paper are summarized as follows. (1) The underwater network model and its energy consumption model with proprietary features in the shallow water are considered as the basis.