# Optimized Clustering Algorithms for Large Wireless Sensor Networks: A Review
## 3 Optimized Hierarchical Based Routing Protocols
### BeeSwarm  
[PERSON] et al. [75] proposed a CI based metaheuristic for energy efficient hierarchical routing named BeeSwarm. It is made up of three phases: BeeCluster, BeeSearch, and BeeCarrier. During the set-up phase (BeeCluster), a similar approach of the ABC is used for the formation of optimal clusters known as Bee Zones (BZs) and the selection of a corresponding CH known as Zonal Head (ZH). To form a BZ, BeeSwarm applies an agglomerative hierarchal clustering, in which two clusters separated by a short distance are combined to obtain the optimal cluster in order to minimize the energy consumption. After clustering of nodes, ZHs are elected for each BZ based on the residual energy and the distance between the BS. The BeeSearch phase occurs after the BeeCluster and consists in the discovery of routes by scout bees. The BeeSearch performs the forward-search to explore the network and the backward-search which maintains different routes between BS and nodes. Meanwhile,once nodes are registered to specific ZHs, ZH prepares a TDMA schedule and transmits this schedule to its registered nodes in the cluster, BeeSwarm uses a LP in other to optimize the transmission. The proposed BeeSwarm approach is evaluated and is compared to routing protocols MRP and to the evolutionary algorithm ERP [76] on several performance parameters. The results have shown that BeeWarm slightly outperforms the other routing protocols in terms of the total number of packet delivered and the packet delivery ratio. It is also observed that BeeSwarm consumes less energy than the two other protocols, thus increases the network lifetime.  
ABC-SD [24]  
ABC- SD is a power efficient cluster-based routing algorithm for WSNs. The proposed approach is also based on the ABC algorithm for efficient searching features. ABC-SD is a semi-distributed approach in which the clustering process is achieved at the BS using the residual energy and the position of nodes and their neighbors. Nevertheless, the data routing is realized by all nodes in a distributed manner. During the set-up phase, the BS which is responsible for built clusters and selected their CHs starts by the construction of the set of candidate's CHs based on position between BS and the residual energy. After the construction of sets, ABC algorithm is executed in order to assign nodes to CH and formed clusters. During the steady-phase a multi-hop TDMA based on a B-MAC which implements a sleep/wake-up mechanism is performed to transmit the gathered data to its corresponding CH, either in a single-hop or in a multi-hop manner, depending on the density of the cluster and the location of the CH. When the clustering process is completed, each cluster member starts a route discovery in order to construct a pre-determined path toward its CH. To evaluate the performance of ABC-SD, authors have compared the proposed algorithm with LEACH, LEACH-C, PSO-C, PSO-HC, and ABC-C. The observations of the results have revealed that ABC-SD has the lowest average energy consumed by nodes and a higher energy efficiency than the other algorithms. It is also observed that ABC-SD minimizes the number of non-clustered nodes, improves the throughput, and maximizes the data delivery compared to the five other approaches.