# Optimization of Clustering in Wireless Sensor Networks: Techniques and Protocols
## 4 The Fundamentals of Clustering
### Recent Issues in Clustering  
Communication is the most energy-intensive task in a WSN. Data communication and intra-node communication account for the highest rate of energy usage in WSNs. Some of the issues and challenges of WSNs with respect to communication include limited battery power, low computation ability, and limited bandwidth [42]. The major problems associated with most WSN clustering protocols are the heterogeneous nature of the nodes, the similar energy levels of all the SNs, and the uniform processing capability and memory of the nodes [43]. This problem does not occur in heterogeneous networks where the nodes are equipped with different bandwidths, energy sources, and processing and computational capabilities.  
1. Energy: Computation and communication activities account for most of the energy usage of the SNs. Energy conservation improves the service life of the WSN due to the dependence of the network life on the battery life of the sensors.
2. Node deployment: This can be done either manually or randomly in a WSN. Manual node deployment involves using various deployment techniques to deploy the nodes manually. This form of deployment requires that the nodes follow a pre-determined path during routing [44]. In random node deployment, the sensors are randomly placed within a sensing environment in an ad-hoc manner.  
Coverage: This is the physical space that can be covered by the deployed nodes; high coverage demonstrates the efficiency of the sensors for monitoring the target area. Connectivity denotes the ability of the nodes to initiate communication with the BS and the neighboring nodes. Network coverage and connectivity ensure the deployment of a sufficient number of nodes to monitor a given area.
4. Data aggregation: As SNs within a given region can sense similar parameters simultaneously, it is likely that they transmit similar data to the CH at the same time, thereby creating redundancy at the CHs [45]. The consequence is energy wastage, as the CHs will need much energy to process the excess data from the nodes, affecting network performance and lifetime.
5. Fault tolerance: Several factors can affect the functioning of SNs in the network, such as energy depletion, environmental and physical conditions, and so forth [46]. The failure of one node can affect the network performance. Hence, WSN protocols must be designed to be fault-tolerant and adaptable to environmental changes such that normalcy can be restored in case of failures.
6. Localization: This is a way of determining the positions of SNs in the network; most of the time, the position of SNs is determined by attaching GPS units to the SNs. However, this is a costly approach that cannot be deployed in all applications [47]. In WSNs, the deployed localization techniques strive towards finding the coordinates of the nodes using cost-efficient techniques.
7. Network dynamics: Most network applications are designed with static nodes, and in such a configuration, node movement is not possible after deployment. Some applications are designed with flexible nodes and BS; nodes in such networks can alter their positions to meet service demands. Mobile node routing is a complicated task due to the frequent changes in the route path and topology of the network.