# Spiral Mobility Based on Optimized Clustering for Optimal Data Extraction in WSNs
## 5 Proposal of Spiral Mobility Based on Optimized Clustering Routing Protocols
### Proposed Model  
In the proposed model of SMOC, a single mobile sink with a fixed spiral pattern is moving in the sensor field to collect data from distributed sensor nodes in the network, while in the case of M-SMOC, four mobile sinks are deployed in the sensor field for data extraction from sensor nodes. Initially, when the nodes are deployed, the sink starts cluster formation. All the clusters are formatted in the order of the center, and in this way, the sink can visit them in a spiral pattern. The sink starts visiting from the center of the network and travels to the next point with the valve of \(X\) and \(Y\) (predefined value) of the sensor field. The sink visits the cluster and waits at the top of the cluster. In the meantime, the CH transmits all the data to the sink and updates the location of the sink to neighbor CHs. Data packets of sensor nodes are neither aggregated nor defragmented unless they reach the sink. After receiving data from the first cluster, the sink moves to the next cluster. Similarly, the sink visits all the clusters in the network, but the waiting time at each cluster is not the same. The sink can stay at any cluster for different amounts of time depending on the number of data packets transmitted by the specific CH, and this variation of time will enhance the data delivery ratio and network lifetime. The operation of SMOC and M-SMOC is divided into time-based iterations, and each iteration is subdivided into two phases; network settling phase and data transmission phase. Figure 4 shows the flowchart of the proposed routing protocols. Figure 3: Network design of spiral mobility executed with multiple sinks for large-scale WSNs. * Network settling phase: This phase generates a specific number of clusters according to the density of the nodes and the size of the network. The sink enforces advanced cluster-formation and executes it in the network, which removes the redundant clusters and broadcasts the exact number of cluster and CHs in the network. The pseudo-code of the advanced cluster formation is shown in Algorithm 1. Figure 4: Flowchart of the proposed Spiral Mobility based on Optimized Clustering (SMOC) and Multiple sink-based SMOC (M-SMOC) routing protocols. * Data transmission phase: After selecting CHs, the actual communication takes place in the data transmission phase, and the sink starts visiting from cluster-to-cluster, making sure that every node is able to communicate with a specific CH. Meanwhile, the sink receives data from the CHs. After collecting data from all the clusters, the sink starts moving in the backward direction, and reverse mobility takes place. From the last cluster, the sink travels from cluster-to-cluster in the backward direction until it reaches back at the center of the network. After that, the sink starts the second round. We use reverse mobility to avoid extra time taken by the sink to arrive at the starting position for the next round. This feature in spiral mobility will enhance the data delivery ratio, because the sink receives the data from CHs twice in one round. Moreover, the proposed algorithm allows member nodes to transmit sensed data directly to the sink if the distance of the CH is longer than the distance of the sink.