# An Improved Energy-Efficient Routing Protocol for Wireless Sensor Networks
## 1 Introduction
This protocol generates two fitness functions to determine the capability to become a CH or relay for each node by only taking their energy consumption into account. However, in the SEECH protocol, every node may be elected to be a CH or a relay, including the nodes closer to the BS, which increases the energy consumption. A learning automata-based multilevel heterogeneous routing (LA-MHR) scheme was proposed in [21]. The LA-MHR utilizes S-model-based learning automata for selecting CHs, while the cognitive radio spectrum is allocated by the BS. In addition, single hop communication among different SNs is replaced by a multi-hop communication approach in the LA-MHR scheme. Since a single communication approach is not suitable for scenes in which the CHs are far from the SNs, this approach requires a large amount of transmission power. The LEACH-Mobile (LEACH-M) protocol is proposed for mobile nodes to improve data transfer success rate [22]; however, the cluster head selection and cluster formation for LEACH-M are similar to the LEACH protocol. Because of the high control overheads, the energy dissipation of LEACH-M is greater than LEACH. The optical LEACH (O-LEACH) protocol divides and links a series of WSNs that is around the distributed fiber sensors (DFS) in the hybrid sensor network with a rectangular topology [23]. Compared with LEACH, this method extends the lifetime of WSNs and exhibits good energy efficiency. However, the energy consumption of O-LEACH is not improved. The stable energy efficient network (SEEN) has been proposed for WSNs [24]. The selection of Cluster Head in this protocol is done on the basis of the residual energy of nodes as well as the distance parameter. In wireless sensor networks, few sensor nodes are equipped with higher processing and communicating capabilities. In [25], an energy consumption-minimizing strategy called LEACH-XMP (LEACH-eXtended Message-Passing) was proposed, which adopts a sophisticated energy consumption model for CH nodes without oversimplification. These protocols aim to merely distribute the energy consumption between the CHand its assistant at the beginning of the first round. This distribution will result in a reduction in the network lifetime. To overcome the drawbacks of conventional methods and further prolong the lifetime of WSNs, we propose a novel improved energy-efficient LEACH (IEE-LEACH) routing protocol in this paper. In the proposed protocol, the threshold setting introduces four parameters including the initial energy of nodes, residual energy of nodes, total energy of the network, and average energy of the network. In the proposed IEE-LEACH protocol, the node closer to the BS than the CH does not take part in the cluster formation. Thus, the protocol can balance the energy load and decrease the energy consumption. Furthermore, the proposed IEE-LEACH protocol compares the energy consumption of single hop and multi-hop communication modes in the data transmission phase. The communication mode with the least energy consumption will be adopted. Therefore, the proposed approach decreases the overall communication cost and significantly improves the network lifetime. The remainder of this paper is organized as follows. Section 2 briefly introduces the system model. The proposed IEE-LEACH protocol is indicated in Section 3. We demonstrate the performance evaluation of the proposed protocol via simulations compared to the conventional protocols in Section 4. Finally, conclusions are drawn in Section 5.