## 1 Introduction
### Significant Approaches towards Acquiring Energy Efficiency  
The above discussion shows that it is not plausible to replenish the motes for some applications such as structural health monitoring, environment monitoring, transportation systems and precision agriculture [6] because of the number of motes, the maintenance cost involved or the remote areas where human intervention is not possible. In a nutshell, it is clear that it is the application of a WSN that decides the fate of a node in the context of its energy consumption. By bearing that in mind, the different approaches for achieving energy efficiency are listed and explained below [7]. **Wireless Communication Optimization:** Radio characteristics decide the energy consumption of nodes. If a node is communicating with the other node, then many factors such as its control on transmission power and different modulation schemes incorporated play a significant role. Cooperative communication and cognitive radio also balance the  
Figure 1: IoT based WSN architecture. energy consumption by focusing on the quality of data transmission. These factors are explained below. **Transmission Power Control:** Wireless communication optimization considers transmission power control (TPC). The maintenance of the level of transmission power of a node at a significant specific level with optimized energy consumption is TPC [8]. The energy efficiency of a WSN is directly dependent on the radio characteristics of the wireless sensor nodes [9]. When the data transmission is high in the nearest and known path due to the optimized cluster head, then it guarantees much better throughput. However, the selection of the optimized cluster head and searching for the best route lead to a rapid reduction in battery power level [10]. **Research Gap:** Due to the application-specific nature of a WSN, the development of TPC schemes becomes a daunting task. There are two prominent factors, distance and the quality of the link, that decide the required level of transmission power to reach the receiver. Link quality has some dependence on physical barriers such as environmental conditions and physical obstacles in the path of transmission among nodes. TPC concerning the link quality among nodes is an energy- efficient approach as it selects the minimum power needed to maintain a qualitative link; most TPC schemes are proposed for single-hop communication. TPC is handled with two processes, i.e., discovery of neighboring nodes and setting up a feedback or acknowledgment system for the nodes that have received messages. There are several thresholds defined for deciding the link quality and handling the neighboring tables that store the information about the neighboring nodes. **Cooperative Communication:** In the recent years of technological advancements, MIMO (multiple input multiple outputs) antenna technologies have outperformed the traditional wireless technologies [11]. While it can be implemented in resource-constrained wireless sensor nodes, the installation of an additional antenna would lead to additional space requirements on the node platform. The circuit becomes complex, and the cost of sensor nodes is enhanced enormously [12]. Consequently, dual-antenna approach implementation becomes quixotic. To resolve this issue, individual single antenna nodes are made to cooperate with the other nodes; hence a cooperative MIMO scheme is implemented. When several such nodes are assembled to form such a structure, it is termed a virtual MIMO. Cooperative communication helps in acquiring energy efficiency in a way that ensures reliable communication among the nodes and the base station [9]. When multiple nodes send data by forming a MIMO structure, it not only speeds the data delivery but also helps in reducing the packet drop in the network. **Research Gap:** The current research demonstrates the cooperative communication framework implemented in the network.