## 2 Related Works
### Topology Reconfiguration and Control and Load-Balancing Mechanism
\begin{table}
\begin{tabular}{p{142.3 pt} p{284.5 pt}} \hline \hline
**Tools** & \multicolumn{1}{c}{**Description**} \\ \hline ATEMU [11] & ATEMU, which was the first command-based simulator based on C, does not provide a Graphical User Interface (GUI). Moreover, its performance rate is extremely slow due to the implementation of sequential sensor nodes despite text-based simulation. It guarantees cycle accuracy; however, only the parameters provided on the different systems can be determined. \\ \hline AVRORA [11] & AVRORA is Java-based and it is capable of the simultaneous simulation of multiple sensor nodes. Each sensor node is implemented by a single thread. Prompt understanding is difficult as a GUI is not provided. \\ \hline GloMoSim [11] & GloMoSim uses Parsec language for parallel simulation of the topology of large-scale sensor nodes. However, as the number of sensor nodes that are to be built in the actual environment provide simple deployment, routing prediction of big sensing data and load-balancing simulation are not possible. \\ \hline NS2 [11] & NS2 is a discrete event simulator that has a module-type approach. Although NS2 has a number of sensor setting functions, the application program model is not sufficient when interaction between the application program and the network is required. Although NS2 has a Network Animator for GUI support, simultaneity is excluded as the event command is called from the file where it was previously stored. \\ \hline NS3 [11] & NS3 provides better performance in the aspect of memory management compared to NS2. However, it is a new simulation tool rather than an extended version of NS2 and it does not support all NS2 models. Consequently, simulation is not possible with incompatible models. Moreover, an analysis function for load-balancing is not supported. \\ \hline QualNet [11] & QualNet is the next version of GloMoSim. It is capable of simulating module scenarios and object models developed by different designers. Although it supports the function of a sensor network, analysis for load-balancing is still required as it only provides limited RF analysis. \\ \hline SENSE [11] & SENSE is a simulator based on C++ with a complex FT, MT, and HT configuration. Although we can use G-Sense for substituting the autonomous visualization tool, it is not appropriate for real-time processing of MSN movement. Therefore, with this simulator, it is difficult for users to detect topology configuration problems for big sensing data. \\ \hline SWANS [11] & SWANS is a Java-based simulator capable of user model definition. Moreover, it can present network communication flow on topology on an interface. However, condition setting for load-balancing in FTs, MTs, and HTs is not possible and it also has the limitation of showing only event-based communication flow. \\ \hline TOSSIM [11] & TOSSIM is a simulator developed at Berkeley University in the United States that simulates TinyOS. Although it is capable of actual movement inference and hardware analysis, simulation of OS and the functions of other sensor nodes is not possible due to TinyOS dependency. TOSSIM has a Java-based TinyViz for a GUI, but it is not sufficient for the movement of dynamic sensor nodes. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Existing topology design and verification tools. topology reconfiguration due to the critical node is expanded to a 2-hop node. Moreover, it shows efficiency according to reconfiguration time in the case of within-range. However, reconfiguration frequently occurs due to critical node creation, which negatively affects the overall topology. Therefore, in this paper, we provide an improved topology by considering not only the critical node, but also the overall topology and each sensor's battery consumption rate. The Simple Distributed Approximation Algorithm (SDAA) [15] removes unnecessary CDS composition nodes as the number comes close to the minimum number of gateway nodes that construct a CDS.