## 1 Introduction  
### WSN  
In general, the wireless sensor network (WSN) contains large number of sensor nodes monitored are controlled by the base station (BS). A major process behind the sensor nodes are data transmission, sensing the devices and computation with limited consumption of power factor as well as it is non-rechargeable in nature. Due to these drawbacks there is still a research gap to increase the energy efficiency and to augment network lifetime [1]. WSN sensors undergone real life data processing too much monitoring. Better climate, industrial, etc., monitoring [2]. The general architectural topologies of wireless sensor networks are shown in Figure 1.  
WSN technology is able to achieve the impossible missions in and around the surface of the earth. As a consequence of enormous success of WSN technology and information communication service, significantly wireless networks transform the globe in to a smaller village in the business world [3]. WSN achieved a new milestone in the following applications such as oceanography, environmental monitoring, agriculture, and engineering. In ad-hoc wireless personal area networks (WPAN) huge numbers of intelligent cost effective battery-powered sensor nodes are produced where it consists of a processor, a radio module, a power supply linked with it [4]. Whereas in WSN, the major component of the sensor nodes is a sensing unit, a processing unit, a transceiver, and a power unit as it is explained in the Figure 2. There are huge architectural models are present in the sensor nodes they are infrared, thermal, seismic, visual which are mainly used for environmental and industrial applications.  
1. Sensing Unit--This unit is mainly utilized to measure the physical distinctiveness of the surrounding by using the array of sensors.
2. Processing Unit--In this section microcontrollers are used to initiate the mission, data processing and control. Because microcontrollers are extremely small in size, they are low powered device and simple, so they are used inside the sensors.
3. Transceiver--The process of this unit is to transmit and receive the information in the wireless medium.
4. Power source--The process of this unit is to supply the power to all the components in the sensor [5].  
Usually, sensor nodes are self-organizing in nature, so it is very suitable for network management. It can create a network by itself, and at the same time guide and monitor the network in an effective way. The major drawbacks are it contains limited power resources,  
Figure 1: Architectural topologies of wireless sensor networks.  
Figure 2: Components of a sensor node.  
processing ability, and storage space. As so to overcome this communication protocols are used [6].  
The communication protocols are sub-divided into five sections of layers for the purpose of packet switching as shown in Figure 3. Those are physical, data link, network, transport, and application layers. The primary functionalities of these layers are sensor deployment, management, authentication, aggregation, and storage. The parameters which can be affected due to this process of protocols in protocol stack are energy efficiency, consumption, and latency. In such case optimization becomes essential to reduce the power consumption. New energy efficient protocols with cross layer approaches are introduced to overcome this problem because conventional approaches are not suitable for this process [7; 8].  
In the other hand, security plays an important role. The major security necessities of wireless sensor network are data confidentiality, data integrity, availability, data freshness, secure localization, time synchronization, and self-organization [9].