Energy-Efficient Routing Algorithms In Wireless Sensor Networks With Prolonged Lifetime

The Internet of Things (IoT) is a novel paradigm that is rapidly gaining ground in the scenario of modern wireless telecommunications. IoT enables network connectivity between smart devices at all times, everywhere and about everything. In this context, Wireless Sensor Networks (WSNs) play an important role in increasing the ubiquity of networks with smart devices. WSNs enable a wide variety of applications, including environmental monitoring, medical treatment, emergency response, outer space exploration, and so forth. In a sensor network, a large number of sensors are deployed in a large area with each sensor capable of monitoring or collecting data from its surrounding environment and pass the information to the sink for remote user access through various communication technologies. Sensor nodes, in such networks, are generally powered by small and inexpensive batteries in expectation of surviving for a long period, where sensor battery replacement or recharge is difficult or even impossible to be performed. Thus, energy consumption is an important factor that has to be taken into account when designing a WSN. Sometimes the optimization of energy consumption is more complicated because it involves not only reduction of energy consumption but also prolonging the network lifetime. The energy optimization can be done by having energy awareness in every aspect of design and operation. Most of significant works in the literatures, about homogeneous and heterogeneous WSNs, have emphasized energy savings as an important optimization goal. However, merely saving energy is not enough to effectively prolong the network lifetime. The Uneven Energy Consumption (UEC) is an inherent problem in WSNs characterized by multi-hop routing and many-to-one traffic pattern. An UEC often results in network partition and reduce network lifetime, which deteriorate the performance. This makes the balancing of energy consumption become a critical importance in the design of a WSN and calls for energy-efficient routing protocols that maximize the lifetime of the network.This dissertation seeks to investigate the problem of UEC and maximization of network lifetime for both homogeneous and heterogeneous WSNs. To achieve this goal, some of novel energy-efficient protocols are proposed. In these proposed protocols, energy consumption among all nodes in the network is balanced in expectation that all nodes should run out of energy at nearly the same time. In the first part of this dissertation, we propose an energy-efficient routing protocol called Fuzzy-gossip protocol that is a modification of conventional gossip protocol. Fuzzy-gossip seeks to investigate the issue of the network lifetime in homogeneous WSNs. It reduces the redundant routing massages that can lead to a significant waste of energy through repeatedly recirculation of redundant information. Fuzzy-gossip is capable of selecting the optimal routing path from the source node to the sink; i.e., selection the best node from the candidate nodes in the forwarding paths by favoring the highest remaining energy and the lowest distance to the sink. To show the effectiveness of the proposed protocol in terms of lessening end-to-end delay and balancing energy consumption, we evaluate and compare Fuzzy-gossip with four routing protocols namely; Gossiping, LGossiping, ELGossiping and FELGossiping protocol in two topographical areas. Simulation results demonstrate that the network lifetime achieved by Fuzzy-gossip could be increased by nearly50%,40%,25%and10%than that obtained by Gossiping, LGossiping, ELGossiping and FELGossiping protocol, respectively.Next, the use of multiple paths between each sensor node and the sink node is considered. It is shown that the network lifetime can be improved by efficiently routing (i.e., balancing) the traffic inside the homogeneous WSN. Therefore, we propose two routing protocols; i.e., Fuzzy_A-star protocol and Fuzzy Artificial Bee Colony Routing Protocol (FABCRP). The proposed protocols are to determine the optimal routing path from the source node to the sink for homogeneous WSNs by favoring some of routing criteria (i.e., remaining energy, minimum hop, and traffic load) and balancing among these criteria to prolong the network lifetime as much as possible.To show the effectiveness of Fuzzy_A-star protocol, we compare it with A-star algorithm and fuzzy approach using the same routing criteria in two different topographical areas. Simulation results show that the network lifetime achieved by Fuzzy_A-star could be increased by nearly27%and23%than that obtained by A-star algorithm and fuzzy approach, respectively.In order to further optimize the performance, FABCRP protocol is proposed. To demonstrate the performance of FABCRP, we compare it with fuzzy approach, ABC, and Fuzzy_A-star protocol in the same routing areas. Comparing the results, it can be seen that the network lifetime achieved by FABCRP could increased by nearly35%,30%and15% more than that obtained by fuzzy, ABC and Fuzzy_A-star, respectively.This dissertation also discusses the bottleneck problem and the UEC problem that have been significantly affected in the lifetime of heterogeneous WSNs, especially in the critical nodes near the cluster heads. For this reason, we propose an energy-efficient protocol for heterogeneous WSNs called Fuzzy Chessboard Clustering and Artificial Bee Colony Routing Method (FCC-ABCRM).FCC-ABCRM begins by presenting a novel clustering method called Fuzzy Chessboard Clustering (FCC). FCC uses fuzzy logic to enhance the performance of the Chessboard Clustering (CC) by determining the optimal cluster heads. ABCRM is used to select the optimal routing path for heterogeneous WSNs, in both intra-cluster and inter-cluster. To demonstrate the effectiveness of FCC-ABCRM, we compare FCC-ABCRM with three well-known approaches, namely Chessboard Clustering (CC) approach, PEGASIS and LEACH. Simulation results show that the network lifetime achieved by FCC-ABCRM could be increased by nearly25%,45%and60%more than that obtained by CC, PEGASIS and LEACH, respectively.Although in this dissertation we have proposed several protocols to overcome the UEC problem and prolong the network lifetime, it should also be noted that lots of parameters should be considered and optimized for practical applications. Experimental demonstrations and further investigations are expected in the near future to evaluate and enhance related protocols.