# An Energy-Aware Method for Selecting Cluster Heads in Wireless Sensor Networks  
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1 Combinatorial and Geometric Algorithms Lab., Department of Mathematical Sciences, Yazd University, Yazd 352, Iran; [EMAIL_ADDRESS] or [EMAIL_ADDRESS]  
[PERSON]  
1 Combinatorial and Geometric Algorithms Lab., Department of Mathematical Sciences, Yazd University, Yazd 352, Iran; [EMAIL_ADDRESS] or [EMAIL_ADDRESS]  
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2 Department of Mathematics, Chabahar Maritime University, Chabahar 545, Iran; [EMAIL_ADDRESS]  
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capabilities, and according to the structure, all have a distributed structure and measure the conditions of their surroundings. Furthermore, the primary task of sensor nodes is to gather the data at regular intervals and transform the information into an electronic signal. This signal is transmitted to the base station through a reliable wireless communication medium. In early 1970, with the advent of microelectronics technology, new sensors were produced, which are inexpensive and have small dimensions and low weights. New raw materials for sensor construction were discovered and identified, and subsequently, a new procedure was introduced for collecting data. The integration of sensors and electronic signalling transformer circuits has provided significant opportunities for most applications [4]. Currently, although decreasing the size and weight and increasing the sensor sensitivity of sensor nodes are the primary goals of research laboratories and various companies, decreasing the size of sensor nodes leads to a reduction of the batteries' capabilities. The most important reason for the advent and development of WSNs is to monitor environments continuously where human accessibility and permanent presence is difficult or impossible. For instance, WSNs are used for monitoring the eruption of an active volcanic mountain, impassable border areas, and bridges. Consequently, recharging or replacing dead nodes is impossible because they are located in an inaccessible environment. As a result, due to the energy limitation of the nodes, lifetime and coverage are the main issues in WSNs' efficiency. Since monitoring the applications requires much time, it is expected that sensor networks' lifetime is sufficiently long. Therefore, it is indispensable to divide an area into several sub-areas. By using this model, if several sensor nodes in each area die, others will almost maintain the network coverage. However, if all sensor nodes in an area die, monitoring the area becomes impossible, and network coverage will be destroyed. Consequently, to prolong the lifetime and maintain the network coverage in WSNs, the energy consumption of the nodes should be reduced, and this solution causes each node to consume energy uniformly. Based on the solution mentioned above, the most significant goal in WSNs is energy consumption management. At first, it is critical to recognize how much energy is consumed in sensor nodes. Some of the energy consumption is beneficial, such as sending and receiving data, processing requested queries, and sending and receiving data queries to neighbour nodes. However, various activities in sensor nodes consume too much energy, as follows [5]:  
1. Idle listening: Listening to inactive channels by several sensor nodes to receive possible traffic leads to idle listening. 2. Collision: The collision occurs when a sensor node receives more than one packet per time unit. All of the packets that lead to the collision should be resent, and this procedure increases energy consumption. 3. Eavesdropping: Eavesdropping happens when a sensor node receives packets that are sent to other nodes. 4. Overhead: Overhead is the minimum number of packets that should be used to send data. Figure 1: A sample of wireless sensor networks [1]. Unprepared node: An unprepared node is a node that is not ready to receive a message sent by other nodes. It is indispensable to know how much energy is consumed in various parts of a sensor to manage energy consumption.