Network Lifetime Optimization And Connectivity Restoration In UWSNs

Underwater wireless sensor network(UWSN)has become one of the enabling technologies for the development of future ocean observation systems(OOSs)and has attracted widespread attention in academia and industry.However,due to the harsh underwater environment,limited on-board energy,unstable link quality and hostile destruction by the enemy,the UWSN could not satisfy the needs of large-scale deployment and applications.In the work presented in this thesis,we investigate on building a long lifetime and robust network topology for the UWSNs.We study the crucial issue to reestablish the network connectivity for the partitioned UWSNs.Firstly,we study the crucial issue to prolong the network lifetime.Based on the analysis on the approaches of extending the network lifetime,we include relay nodes(RNs)to the network and re-allocate the data flows between nodes in order to prolong the network lifetime.We formulate the problem as an optimization problem with a novel heuristic scheme proposed and designed,which is named as Alternative Flow and Relay-node Adjustment(AFRA).Extensive simulations demonstrate that the proposed scheme can offer an outstanding performance comparing with traditional algorithms.Secondly,we investigate the issues for the enhancement of the network robustness.The objective of this work is to enhance the network robustness and try to prolong the network lifetime as much as possible.The problem formulation is presented as an optimization problem with a heuristic algorithm proposed which is named as a Topology Control Algorithm based on Optimal Rigid Graph(TCA-ORG).It takes use of the property of optimal rigid graph to design a weight function for each edge.Extensive simulations have proved the effectiveness of the proposed algorithm.The network topology constructed by our algorithm has a higher robustness with a higher efficiency than other approaches.Lastly,we study the issue to reestablish the network connectivity for the UWSNs.The objective of this research is to reconnect the partitioned network with the minimum number of RNs.The problem is formulated as an optimization problem with an original heuristic scheme designed in this work,which is named as Alternative Tree Construction and Fermat-point Selection(ATCFS).The results of the simulations demonstrate the effectiveness of the ATCFS scheme.In summary,this thesis works on the topology management of the UWSNs.Based on the characteristic of the UWSNs,we propose the strategies to prolong the network lifetime,enhance the network robustness and restore the network connectivity.Simulation results have proved the effectiveness of the proposed solutions.