# Cluster-Based Routing Protocol with Static Hub (CRPSH) for WSN-Assisted IoT Networks
## 2 Literature Review
HRPM's unicast method is used for delivering the data from the source to the AP tree, and GMR's broadcast-based forwarding method is used for AP to member tree to reduce transmission numbers. AP monitors destination IoT devices in every cell, and these are selected by using the localized neighbor selection method of the GMR. The trees in HGMR are not overlay as in HRPM. [PERSON] and [PERSON] propose a grid-based multipath routing protocol (GMCAR) that avoids congestion and supports QoS traffic for WSN [41]. This protocol is proactive, hierarchical, and supports multipath. The protocol consists of three phases: grid formation, building routing tables, and data transmission phases. The entire network is divided into small, square-shaped grids of predefined size, containing a master and nonmaster IoT device. It is the first protocol to use the concept of finding the diagonal paths between the master IoT device and the IoT hub. It also considers the density of IoT devices as a decision factor for data forwarding. The master IoT device is responsible for data routing from nonmaster IoT devices and other master IoT devices to the IoT hub. A routing table is built for each master IoT device to know other masters' IoT device positions to send the data diagonally until it reaches the IoT hub. The IoT hub sends a flooding message to enable master IoT devices to find the paths from the grid to the IoT hub. Master IoT devices collect the data from grid members and select the next master IoT device to send the data. This process is continued until the energy of the master IoT device is exhausted. The master IoT device selects a new IoT device based on residual energy. The GMCAR uses two routing techniques for high and low traffic to boost network lifetime. An energy-aware grid-based routing technique named EAGER for WSN is proposed by [PERSON] and [PERSON] [42]. Grids are constructed in the network, and each grid is assigned with a unique grid ID. An IoT device is selected as a grid head in each grid, which has information about the neighboring grid heads. The TDMA technique is used for keeping the grid heads active depending on the sum of coordinates. The grid head of the source IoT device sends a request packet for path building. The IoT hub's Local Grid Head (LGH) replies with a reply packet that reached the source's LGH, so this path transmits the data. When the IoT hub moves to another location, the IoT hub's path is extended by the IoT hub, and rerouting is used for constructing a path to the IoT hub. [PERSON] et al. proposed VGDRA, where the network area is divided into grids containing equally sized cells [43]. Cell headers are the IoT devices close to the center of the cell. For the communication between neighboring cells, gateway IoT devices are elected. Cell headers can keep the information regarding the IoT hub's present location by constructing a virtual backbone structure with gateway IoT devices. Data communication takes place between member IoT devices and their closest cell header. Cell headers collect the data from member IoT devices and transfer them to mobile IoT hubs. The IoT hub flows in the network to collect data from the border cell header. The route's re-adjustment can be performed by a border cell header, which is very close to an IoT hub. The network reliability is the main concern for the existing routing protocols such as PCMRP. It creates a multipath by flooding control packets across the network. This is a significant contributor to the increase in control packet overhead. Additionally, the multipath is reconstructed if any device becomes the source. This adds to the protocol's overhead [44]. The REDCL method prioritizes the selection of a fewer number of active reporting nodes (ARNs) in hotspot areas over the selection of more ARNs in non hotspot areas. The REDCL method converges the paths of several ARNs monitoring an event outside of nonhotspot zones and sends them to the hub after data aggregation. The hotspot area's ARNs are unable to transfer data directly to the hub.