# Optimization of Clustering in Wireless Sensor Networks: Techniques and Protocols  
[PERSON]  
1 Center for Cyber Security, Faculty of Information Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600, Malaysia; [EMAIL_ADDRESS] (A.M.J. ); [EMAIL_ADDRESS] (A.H.M.A. ); [EMAIL_ADDRESS] (H.S.) [PERSON]  
1 Center for Cyber Security, Faculty of Information Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600, Malaysia; [EMAIL_ADDRESS] (A.M.J. ); [EMAIL_ADDRESS] (A.H.M.A. ); [EMAIL_ADDRESS] (H.S.) [PERSON]  
1 Center for Cyber Security, Faculty of Information Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600, Malaysia; [EMAIL_ADDRESS] (A.M.J. ); [EMAIL_ADDRESS] (A.H.M.A. ); [EMAIL_ADDRESS] (H.S.) [PERSON]  
1 Center for Cyber Security, Faculty of Information Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600, Malaysia; [EMAIL_ADDRESS] (A.M.J. ); [EMAIL_ADDRESS] (A.H.M.A. ); [EMAIL_ADDRESS] (H.S.) [PERSON]  
2 Department of Information and Computer Science, College of Computer Science and Engineering, University of Ha'il, Ha'il 81481, Saudi Arabia; [EMAIL_ADDRESS] (Z.G.A-M.); [EMAIL_ADDRESS] (M.S.A.) [PERSON]  
3 Department of Computer Engineering, College of Computer Science and Engineering, University of Ha'il, Ha'il 81481, Saudi Arabia; [EMAIL_ADDRESS] (Correspondence: [EMAIL_ADDRESS] (Correspondence: [EMAIL_ADDRESS] (Correspondence: rosilah@ukm. more [2; 3]. The deployment of WSNs is mainly in areas that may not be easily reachable by humans. An interesting research aspect of WSN is related to energy usage and balance in the network. The limited and non-rechargeable nature of node power supplies has driven research into new ways of improving the energy balance and energy efficiency in WSNs [4]. The lifetimes of sensor batteries are limited, and efforts are being made to enhance these sensors' service lives by designing energy-efficient routing protocols. Routing is a tedious task in a WSN, as it is the basic feature that differentiates WSNs from other ad hoc wireless networks. Energy-efficient routing methods are necessary for a WSN to transfer sensed data from the Sensor Node (SN) to the BS; this will improve the service life of the network. Sensor nodes in WSNs are normally grouped into clusters, and this clustering method is used in WSNs to ensure the scalability of the network. It also guarantees efficient resource use and management of limited network resources, saving energy and conserving the stability of the network [5]. Clustering schemes are deployed in sensor networks to ensure efficient resource usage and reduce communication overheads, reducing the system's overall energy usage and keeping interference low among the SNs [6]. According to [7], clustering routing is mainly deployed to reduce the data transmission rate via the mechanism of information pooling in the Cluster Head (CH). This mechanism reduces communication-related energy usage, hence decreasing energy demand by the SN. Another reason for deploying clustering is to improve load balancing, thereby prolonging the service life of the network. Clustering strives towards improving the network lifetime by ensuring balance in the duties of the CHs. Most types of WSN rely on cluster-based protocols to reduce energy consumption by the SNs. These clustering techniques used in WSNs are based on several optimization methods for efficient handling of clustering operations. To understand the existing problems in this research area (WSN clustering), conducting a literature review seems essential for providing a more profound knowledge of the different clustering methods and their limitations. This review aims to examine the existing clustering techniques used to improve the performance of sensor networks based on different design characteristics and optimization methods.