## 2 Related Work
Actually, both TADC and RIADC satisfy the coverage for topology control through altering the sensing radii of nodes. However, the only difference is TADC only adjusts the sensing radius of one node at each round while multiple nodes in RIADC may increase their sensing radii in each round simultaneously. Because to UWSN is typically an opportunistic network, QoS-based target is a focus issue that we are always concerned about. As we know, the links for the instant message in UWSN are always unstable and cut off [14; 15]. The probabilistic multipath routing behavior driven by the opportunistic routing protocols is modeled in [15]; simultaneously, the probabilistic-based multipath centrality metric is proposed to measure the importance of UWSN to the data delivery task. It can be used to guide topology control to make better network performance because of identifying the critical nodes. In [16], to gain the preferable throughput efficiency of the network, the improved distributed topology control (iDTC) and the power adjustment distributed topology control (PADTC) are, respectively, proposed to guarantee the delivery of data by dealing with communication void problem of geographic opportunistic routing. With the depth adjustment and power adjustment of a void node, both protocols can obtain better energy efficiency and perform minimum displacement in the case of a void node while maintaining the same throughput. On the other hand, due to the characteristic of water flowing, node mobility is another critical factor in UWSN [17]. Therefore, many kinds studies discuss mobility-based topology control techniques. [PERSON] et al. [18] and [PERSON] et al. [19] proposed either mobility models for specialized applications or mobility-targeted topology control algorithms for movable UWSN. In addition, topology control can also contribute to other aspects of UWSN, e.g., localization technique. Usually, the unlocalized node can find its location by utilizing the spatiotemporal relation with the reference nodes; however, most nodes lack the required number of the reference nodes in the sparse scenario. To address this problem, [PERSON] et al. [20] proposed an opportunistic localization by topology control (namely, OLTC) for sparse UWSN. In OLTC, some reference nodes are discovered through the topology construction process, while a game-theoretic model based on single-leader-multi-follower Stackelberg game for topology control is established to describe the relationship between the unlocalized and the localized nodes. Consequently, with the help of OLTC scheme, the localization coverage and the energy-efficiency can be promoted better than before. In summary, topology control is indeed one of the worthy techniques for UWSN to study, even if research scholars focus on the different points and targets. From almost all literature, the energy-efficiency is still the common point which is only concerned about for the whole network. However, the current study for topology control in UWSN has the following drawbacks. (1) The overly idealized network model: The current assumed network model should be application-oriented built for the real environment. (2) Topology control scheme without preferable load-balance: Since energy is the key point for the underwater IoT-based application, topology control without preferable load-balance cannot ensure energy conservation and limits the further application. Consequently, we propose a topology control algorithm with energy balance (namely, TCEB) for UWSN, which contributes to a better energy-efficiency under such complicated underwater communication mode. The main target is to make underwater network load-balance and consume energy efficiently so that the lifetime of the network would be prolonged.