# Dynamic Group Management Scheme for Sustainable and Secure Information Sensing in IoT
## 2 Related Work  
### LEACH Routing Protocol  
The LEACH protocol introduced the cluster-based routing protocol that allowed the sensor nodes to consume power equally with communication distance by taking advantage of the fact that the power of sensor nodes would increase in proportion with communication distance [11].  
The nodes arbitrarily elect cluster headers in the LEACH routing protocol and they form each cluster through those elected cluster headers. Furthermore, the sensor groups are formed based on the consumption rate of energy generated when communicating with the cluster headers. Therefore, the groups are formed dynamically based on the elected cluster headers in the LEACH routing protocol. The group-based communication shall be conducted accordingly.  
Those nodes included in a cluster collect data and transmit these collected data to a cluster header. A cluster header organizes the data transmitted by nodes, transfers it to the base station in the end, and communicates with the base station. On this account, they consume more energy compared to the other nodes. Also, there might be an adverse effect on the entire sensor network when a majority of tasks are concentrated on a particular node. The LEACH routing protocol prevents the phenomenon that tasks are concentrated on a particular node through the method of electing a new cluster header in each round in order to distribute energy consumption that is otherwise concentrated on a particular node.  
The LEACH routing protocol elects a cluster header among the nodes that have not become a cluster header. These newly elected cluster headers form a new cluster with the remaining nodes. Herein, the time of forming and disbanding a new cluster is expressed as \"round\". A round is repeated periodically; thus, all the nodes in a region are selected once as a cluster header. As a result, they distribute the energy consumption that is concentrated on the cluster headers. After all the nodes have become a cluster header, all the nodes are again qualified to become a cluster header. This cycle is called \"group of round\". In regard to the time of LEACH routing protocol, all the nodes in a network should be synchronized.  
The LEACH routing protocol elects a cluster header through a probability-based algorithm. In the process of electing a cluster header, those sensor nodes that have never become a cluster header in a group of round take part. No special message is utilized in the process of electing a cluster header in the LEACH routing protocol. The purpose of the LEACH routing protocol is to enhance the energy efficiency of sensor networks and increase the overall lifetime of networks by allowing for equal energy consumption through distributing the energy consumption concentrated on a particular cluster-forming node.  
The LEACH routing protocol elects a new cluster header for each round in order to consume energy equally, which would otherwise be concentrated on a particular node. At this time, those cluster headers that have been elected in the current group of round are not able to participate. Therefore, the probability of being elected as a cluster header will increase after each round.