## 2 Related Work
### Reviewing Mobile Sink Routing Protocol  
There are many approaches for issue of routing in a wireless sensor network with mobile sinks; the most important method that has been extensively used is hierarchical mobile sink routing protocols. The purpose of these methods is reducing the load of sink position notification to the network by creating a layer of hierarchical nodes imposing different dynamic roles to sensor nodes. In addition, we introduce several methods. Figure 6: General schematic of a sensor node. The LBDD (line-based data dissemination protocol) [32] defines a wide vertical strip of nodes that are horizontally centered on the area of deployment. The nodes positioned inside of the band are called in-line nodes. This band represents an area of appointments for queries and data storage (Figure 7). The nodes can access the line by a straightforward mechanism [33]. The LBDD protocol [34] assumes that each node knows its geographical position and the coordinates of the interest area. LBDD uses then a geographic routing. The operation of LBDD consists of two main steps:  
* Dissemination: when a node detects a stimulus, the data is generated and sent to the nearest inline-node;
* Collection: to collect different data, the sink sends a perpendicular query to the band. The first in-line node which receives the query will propagate it in both directions of the band to attain the nodes with the required data. The data will be then sent directly to the sink. Line-based data dissemination is yet relying on dissemination for disseminating the data search along the line. The line must be extended enough to reduce the main points. Therefore, particularly for large grids, in-line current may considerably increase total energy. A railroad [30] constructs a structure called the rail, which is a closed loop of a strip of nodes, shaped to reflect the outline of the network (Figure 8). The nodes on the rail are called rail nodes. When a node has sensor data, it sends some information about this data to the nearest rail node that constructs a station, which is a portion of the rail centered on the rail node. The sink searches the rail for data and when it attains to station node, it notifies the source from sink position and data is directly sent to the sink. One of the key differences of railroads with line-based data dissemination is that the sink search is traveling on the rail by single molds instead of dissemination. To ensure that a search with a node is faced with data, stations must cover the width of the rail. Using the stations reduces the need to extended disseminations in the rail, and it is considered an advantage over line-based data dissemination together with assisting the protocol scalability. However, it is expected that delays for delivering the railroad data is higher than line-based data dissemination; this is because searches must travel by a much longer structure. Once a search attains to a station, the source node must be informed from the sink position to begin data dissemination, because data is stored in the database in the stations, and therefore increases the delay for data delivery. Figure 8: Railroad architecture. Figure 7: Line-based data dissemination (LBDD) architecture. Ring Routing [31] creates a ring structure and its purpose is combining the easy accessibility of grid structures with the capability of easy change in the column structures (Figure 9). It also reduces the redundancy of routing control packages by combining the minimum quantity of nodes in the ring structure and uses a simple and efficient mechanism for sharing the sink position notification among ring nodes. A ring might be created with low overhead, like structures used in region-based methods (for example, line-based data dissemination, railroad). On the other hand, Ring Routing relies on a minimum inefficient dissemination value that is extensively used in region-based protocols. Ring Routing is a targeted routing protocol for wide-scale wireless sensor network located externally with fixed sensor nodes and a mobile sink.