## 3 SLS Scheme  
An FT, MT, and HT with the SLS application function are shown in Figure 1. This operation not only considers the number of sensor nodes connected within the constructed topology for big sensing data transfer, but is also capable of bypassing it by considering the battery consumption rate, which eventually contributes to the maximization of the overall topology lifespan.  
The sensor nodes with SLS implementation are largely composed of sensor id, observation, base information, and current information; the XML scheme is presented in Figure 2. This type of XML scheme is used for load-balancing in FTs, MTs, and HTs, and is aimed at the maximization of the overall topology lifespan for big data of sensors.  
Figure 1: Load-balancing of SLS.  
Each SLS-applied sensor operates in two ways according to the threshold setting of the battery consumption rate and battery remains. The first case, where the threshold is not determined, operates as follows:  
1. The battery consumption rate per unit time is computed in the initially composed topology. The battery consumption rate is calculated by using the battery remains after the implementation to active and sleep modes with the time that the sensor first operated as a standard, which can be expressed as in Equation (1). \[Battery_{consumption}\ =\ \frac{Battery_{total}-Battery_{current}}{CurrentTime- StartTime}\] (1)
2. The battery consumption rate is compared to that of other connectable neighboring sensor nodes. The basic method of comparison is to sending its own battery consumption rate during communication for connectivity maintenance. Here, the comparison is conducted when transferring sensing data or routing sensing data from other sensor nodes.
3. Referring to the battery consumption rate comparison results in 2, sensing data are transferred to the sensor nodes that have lower battery consumption rates.
4. The received sensor nodes iteratively perform 1, 2, and 3 until the transfer to the sink node is complete.  
Figure 2: XML scheme of sensor nodes for SLS.  
If the threshold of the battery consumption rate or the battery remains is defined, the operation occurs as follows:  
1. The battery consumption rate per unit time is computed in the initially composed topology. The battery consumption rate is calculated by using the battery remains after the implementation to active and sleep modes with the time that the sensor first operated as a standard, which can be expressed as in Equation (1).
2. If \(\mathit{Battery}_{\mathit{consumption}}\) is equal to or larger than the threshold value, proceed to 3. Otherwise, sensing data are transferred to the connected sensor nodes. If it is not larger than the threshold value, 1 and 2 are iteratively performed until the received sensor node transfers to the sink node, routing the sensing data.
3. The battery consumption rate is compared to that of other connectable neighboring sensor nodes. The basic method of comparison is to send its own battery consumption rate during communication for connectivity maintenance. Here, the comparison is conducted when transferring sensing data or routing sensing data from other sensor nodes.
4. Referring to the battery consumption rate comparison results in 2, sensing data are transferred to the sensor nodes that have lower battery consumption rates.