Research On Lifetime Prolonging Algorithms For Wireless Sensor Networks

Wireless sensor networks (WSNs) has become a hot spot with the development of microelectromechanical systems, embedded computing, techonolgy of wireless communication, andso on. WSNs is the basement of the internet of things, it centers the data, has the function ofinformation sensing and cooperative accessing, and can be applied in many fields, such asnational defense, intelligent traffic, intelligent building, environmental monitoring, andmedical care. At the same time, WSNs has some feathers different from traditional Internet,for example, nodes of WSNs are dense, resource (energy, computer power, andcommunication power) of nodes are restricted and the topology of WSNs is active, whichmake the primary goal of WSNs’s algorithm design is enlonging the lifetime of WSNs. Timesynchronization algorithm of heterogeneous WSNs, nodes scheduling algorithm,coverage-hole repairing algorithm, and routing algorithm are researched in this paper, thecontents and achievement are as follows:(1) Aiming at that there are some heterogeneous nodes in special applications,cluster-based time synchronization algorithm of heterogeneous WSNs (CTSA) is proposed inthis paper. In every round of CTSA algorithm, time synchronization is launched by sink node,every heterogeneous node sends cluster head request message to sink node when it receivesthe time synchronization launch message, and take itself as a cluster head when it recesivesthe acknowledgement sended by sink node.Then, every cluster head broadcasts electedmessage in the net, common nodes select the nearest cluster head as their cluster head and jointhe cluster. Time synchronization begins firstly between sink node and cluster heads, and thenbegins between cluster heads and common nodes. The components of transmission delay ofsynchronization message between sender and receiver are analyzed and computed,consequently, the time offset of nodes are obtained, and the frequency drift are computed bylinear regression method. Simmulation results indicate that CTSA algorithm has highersynchronization rate and synchronization precision, longer lifetime and lower energyconsumption than FTSP algorithm in heterogeneous WSNs.(2) Aiming at that the exiting nodes scheduling algorithms can’t keep the initial coverage of nets, coverage-preserving nodes scheduling in clusters for wireless sensornetworks (CPNSC) is proposed in this paper. CPNSC algorithm utilizes the same method offorming clusters with LEACH algorithm, while every cluster node establishes the informationform of common nodes, the distance form between every two common nodes in its cluster,and judges every common node is a redundant node or not in the orde of node’s ID, if onenode is a reduant one, the cluster marks it in the information form. After cluster headcomputes all the common nodes in its cluster, it broadcasts the nodes information form in itscluster, every common node in the cluster schedules itself in accordance with the form.Simmulation results indicate that CPNSC algorithm has different performance with thedifferent sensing radius, while if the sensing radius reaches a fixed value, the coveragevariation will not apparent. This is because the performance of CPNSC algorithm is related tosensing radius and the size of cluster in the same time, if the sensing radius is so large, thesize of cluster will play a key role in CPNSC algorithm. Simmulation results also indicate thatif there are no enough redundant nodes, CPNSC algorithm has an advantage over E-LEACHalgorithm in coverage and energy consumption.(3) Aiming at that the exiting coverag-hole repair algorithms must executed repeatedly inevery round, coverage-hole repairing algorithm towards nodes failure in clusters of WSNs(CHPA) is proposed based on CPNSC algorithm. In CHPA algorithm, when any commonnode is about to failure because exhausted of energy, it sends failure message to cluster headimmediately, and the cluster head activates the redundant node within the sensing range offailure node which has the most boundary nodes as neighbor nodes. Because CHPA algorithmis realized on the basis of CPNSC algorithm, the performance of CHPA algorithm is alsorelated to sensing radius and the size of cluster, and the simmulation results indicate thatCHPA algorithm has an advantage over3MeSH in coverage, energy consumption per roundand time consumption per round.(4) Aiming at the problems of LEACH algorithm, an energy efficient routing algorithmbased on cluster (EERA) is proposed in this paper. In EERA algorithm, many factors whichcan equilibrium the energy consumption of WSNs are considered in the process of electingcluster head, routing between cluster heads, and common nodes joining in clusters. For example, in the process of electing cluster head, residual energy and the number of neighbornodes of every node are consided; in the process of routing between cluster heads, distancebetween one cluster head and the next cluster head and the residul energy of the next clusterhead are considered; in the process of common nodes joining in clusters, the distance betweenthe common node and cluster head and the energy consumption coefficient of transmittingmessage by the cluster head are considered. Simulation results indicate that EERA algorithmhas an advantage over LEACH algorithm, LEACH-EE algorithm and EERP algorithm inlifetime, energy consumption of cluster heads, and energy consumption of whole net.