Research On Energy-efficient Optimization Strategy For Wireless Sensor Networks

Wireless Sensor Networks are self-organization and multi-hop routing information transmission networks which composed of a large amount of resource-constrained micro-sensor nodes with functions of data acquisition,data processing,data storage and wireless communication.They had been extensively used in environmental monitoring,smart home,intelligent agriculture,resource exploration,military defense,and so on.However,sensor nodes in WSNs are usually powered by batteries with limited energy,and often deployed in inaccessible and hostile environment.Furthermore,sensor nodes are widely distributed in huge amount.Therefore,they can't be timely and effectively replenished due to energy depletion,which led to decrease and disappearance of the network functions,and affect economy and practicability of the network.Consequently,it is one of the most important issues to effectively improve energy utilization and prolong network lifetime in design and application of WSNs.Energy-efficient optimization strategies are studied about target coverage,routing protocol and data transmission in WSNs,and relevant solutions are proposed in this paper.The main research issues and contributions are summarized as follows:1.The target coverage problem of maximizing network lifetime is discussed,according to existing target coverage algorithm based on sensor node set partition,a heuristic target coverage algorithm for maximizing network lifetime is proposed,and the 'round' is used to be the metric of network lifetime.The concept of key coverage target and the principle of priority coverage of key coverage target are introduced to obtain the optimal covering subset in each round.Then,the locally optimal solutions of network lifetime are obtained,and the global optimal solution is approached successively by the locally optimal solutions.Moreover,according to the principle of maximum sensor nodes utility to activate sensor nodes,the energy consumption of key coverage targets is reduced,and the purpose of prolonging network life is achieved.The simulation results show that the proposed algorithm has a certain improvement in network lifetime,compared with the MC-MIP and MUA-WPT.2.The characteristics and disadvantages of the cluster-based hierarchical routing protocol are discussed,combining the advantages of chain-based hierarchical routing protocol,an energy-efficient hierarchical routing protocol for WSNs,which integrates cluster and chain,is conceived.The leveling phase is introduced to classify nodes which close to the base station are divided into level L1 and the distant ones into level L2.L 1-level nodes are chained to construct a data transmission chain,and the node with most residual energy is chosen to directly communicate with the base station.Clustering is carried out on L2-level nodes,considering the residual energy of nodes on the basis of LEACH,the probability that nodes with more residual energy are elected as cluster heads is increased to ensure network load balancing.According to the distances between the cluster heads and L 1-level nodes,the residual energy and the number of neighbor nodes of L1-level nodes,an optimal Ll-level node is elected for each cluster head as the direct relay node for data transmission with the base station,the number of nodes directly communicate with the base station and the distance between the cluster head and the base station are optimized to achieve the purpose of balancing and reducing the energy consumption and prolonging the network life.The simulation results show that energy consumption and network lifetime had been improved by the proposed routing protocol,compared with LEACH,PEGASIS,NF-LEACH,CRA and PEG-ACO.3.The problem of maximizing transmission rate in WSNs is discussed,combining the advantages of network coding in throughput optimization and efficiently secure data transmission.When the information collected by multiple sensor nodes is sent to multiple users,on the premise of ensuring data confidentiality in the process of transmitting,the joint optimization design of transmission rate allocation,transmission topology selection and secure linear coding is studied to maximize transmission throughput and save the network energy.A LP(Linear Programming)algorithm based on linear programming is designed to solve the problem of multi-stream secure multicasts(MSM)with fixed source points.The transmission rate of each multicast data stream is determined by LP algorithm,which can maximize the total weighted transmission rate under security conditions.In addition,an integer linear programming model is established for the MSM problem with unfixed source points,and then an LPR(Linear Programming Relaxation)algorithm is designed based on the linear programming relaxation.Although the optimal solution of MSM problem can't be obtained by LPR algorithm,the transmission rate of the source and each data stream of each multicast are determined by LPR algorithm,which can achieve a higher total weighted transmission rate.The upper and lower bounds are designed respectively for the MSM problem with fixed and unfixed source points in the simulation,LP algorithm and LPR algorithm are compared with the upper and lower bounds under different parameters.The simulation results show that the proposed algorithms can effectively guarantee the secure data transmission,improve the throughput and energy utilization,and achieve the purpose of prolonging network life.