Research On Energy-efficient Cluster-based Topology Control For Wireless Sensor Networks

Wireless sensor networks(WSNs) have been widely used in military investigation, environmental monitoring, medical protection, Internet of Objects and other fields as a new way for information collection and processing. Topology control is a key technology in WSNs, which can not only improves the network topology, but also provides the basic platform for other network technologies and applications. As a complex network with energy restricted, WSNs have to face the energy efficiency which is the most important for it. Topology control algorithm can construct the efficient network topology to reduce and balance energy consumption of nodes, so as to prolong the network lifetime. Comparing with the plane topology control, the networks based on hierarchical clustering topology control can be more effective in eliminating redundant sensing data, simplifying network operations and data transmission, reducing network energy consumption and prolonging the lifetime of WSNs. Especially in managing and scheduling large-scale network, the networks based on clustering topology have a great advantage than others. In this paper, the searches are mainly focus on the energy consumption optimization methods for the WSNs based on hierarchical clustering topology control so as to improve network energy efficiency. The main studies include the following aspects:(1) For the limitations of cluster head rotation strategies existing in WSNs, the paper analyzes the characters of time-driven and energy-driven cluster head rotation strategies. After analyzing and comparing the network energy efficiency of two strategies in networks, we propose a energy-time hybrid cluster driven head rotation strategy. The hybrid cluster head rotation strategy can avoid the excessive system header frame in single time-driven rotation strategy and the defect frequent rotation of cluster heads in the end of energy-driven rotation strategy. Simulation results show that the hybrid rotation strategy can efficiently increase network energy efficiency and prolong network lifetime.(2) For the cluster size control in clustering topology control, we have studied from energy consumption as well as the optimal clustering coverage in this paper. Firstly, from the perspective of optimal energy consumption, we derive and analyze the optimal cluster size estimation methods in single-hop communication and multi-hop communication WSNs, and we derive the relationship among the optimal cluster size, the number of and distribution the distribution density of sensor node; secondly, aiming at the optimal coverage and connectivity in the networks based on cluster, we deduce the conclusions for the cluster size calculation. Finally, comparing the methods above, we prove that the networks can achieve higher energy efficiency when the nodes distribution is sparse. The research results above have very important significance in control cluster size control in clustering WSNs.(3) For the energy hole problem in the multi-hop communication networks based on clustering topology, an unequal cluster protocol has been set up in this paper. By analyzing the energy consumption on the cluster head, the article has proved that the cluster is not always reduced radius along with its distance decreases to Sink when the network nodes achieve the lowest average energy consumption. Based on the results above, an unequal cluster protocol which is different from the unequal cluster protocols current has been designed. The experiments prove that this cluster protocol which aims at alleviating the energy hole problem improves WSNs’ energy efficiency and has higher energy efficiency.(4) The unequal cluster protocol can only reduce but not eliminate the impact of energy hole problem because of the inherent characteristics of multi-hop communication in WSNs with even nodes distribution. To solve this problem, a non-uniform sensor nodes distribution strategy based the unequal cluster above has been proposed. According to the distance between the sensing area and Sink, the algorithm calculates the nodes distribution density and schedules the sensor nodes by sleeping-waking mechanism. Theoretical analysis and experimental results show that, the proposed method can effectively improve network energy efficiency and prolong network lifetime compared to existing non-uniform node distribution strategy. The energy hole problem can be solved absolutely with the lowest cost of the network.(5) The topology control and data routing are closely correlative and good routing protocol can make up for some inherent defects of WSNs’ topology control. For the issues of imbalance energy consumption in WSNs, the energy efficient routing protocols based clustering topology are designed in this paper. For small-scale wireless sensor networks, an energy balance data routing protocol has been proposed which tries to solve unbalanced energy consumption problem with the lowest system frame cost. For large-scale wireless sensor networks, the article introduces routing matrix by linear optimization method to calculate the optimal routing mechanism, so that each cluster head shares data relay task more reasonably and achieve traffic load uniformly. The simulation has proved that this routing protocol can effectively solve energy efficiency problem of data transmission in large-scale wireless sensor networks.