## 1 Introduction  
A wireless sensor network (WSN) is composed of sensor nodes meant for a specific purpose and deployed in the given geographical area. The main operations involved at each sensor node are sensing, processing, and communication. Each sensor node in the network senses the physical environment, processes the sensed parameter values (such as ambient light, pressure, humidity, etc. ), and sends these data to the base station (BS) through cluster heads. Further, the BS (which is the sink node) communicates the sensed data to the control station through the Internet, as shown in Figure 1. At later stages, the data can be viewed and interpreted by the user application, and deeper data analytics are performed on the stored data at servers. In industry automation applications [1], the role of WSNs becomes essential, as it does in all the advanced applications of the Internet of things (IoT) and the Industrial IoT in their perception layer. In Figure 2, a sensor node's hardware architecture is presented; it mainly consists of sensing modules, a processing unit, a communication unit, and a power unit. It has components including a sensor node, a power source, an analog-to-digital converter (ADC), a controller, a memory unit, and a transceiver. The sensor circuitry converts the physical sensed quantities into equivalent electrical signals. The ADC module converts the analog values or signals into their digital equivalents and feeds them to the controller. The controller processes the signals which can be feasible for transmission over the communication network, as well as for storage in the memory unit. The transceiver module is used to send and receive data simultaneously. Every sensor node can communicate with other sensor nodes, as well as with the BS, via direct links or through multi-hops. Though there exist two types of WSN architectures, namely, layer-based and cluster-based, most of the practical applications use cluster-based architectures. In cluster-based architectures, there exist cluster heads, which take responsibility for collecting sensed data from cluster members and perform data fusion before sending them to the BS. The data fusion process eliminates redundant data transmissions and improves network lifetime. The role of CH is changed among sensor nodes based on certain criteria to avoid energy depletion at the sensor nodes. In WSNs, each sensor node identifies the occurrence of an event within its sensing range and transmits this information to its neighborhood present in its communication range. This information is finally sent to the sink node through multi-hop communication. The information should arrive at the sink node along the optimal path and should avoid travelling through uncovered regions of the network. Therefore, the strategic deployment of sensor nodes plays an important role in maintaining connectivity and coverage optimization. In the pre-determined or pre-planned deployment method, the sensor nodes are placed at pre-defined coordinates to achieve maximum connectivity and coverage. But such  
Figure 1: Application-oriented WSN architecture. deployments are not suitable for the military and hard-to-reach applications. Therefore, the coverage and connectivity in randomly deployed WSNs draws the attention of researchers in nascent works. In modern data-driven applications of WSNs, the best network coverage and connectivity are essential aspects for seamless data collection and transmission. WSN coverage can be measured in terms of area, point, or boundary. Area coverage aims to cover the whole region of interest (ROI) with fewer sensor nodes. Point coverage tries to focus on individual target nodes in the ROI. Boundary coverage prevents infiltration by covering certain paths in the ROI including the network boundaries. Point coverage in WSNs is used to monitor the target nodes in particular regions of the network and be observed by at least one anchor node. The optimal selection of anchor nodes leads to increased lifetime of the network.