Research On Topology Control Algorithm In WSN

Due to the bad deployed conditions, special application areas and limited hardwareresources, Wireless Sensor Networks (WSN) face a series of problems of how to monitor thenetwork topology remotely, use the battery energy effectively, save the energy consumptionand prolong the network lifecycle, etc. Therefore, Topology Control plays a very importantrole in WSN. In recent years, researchers in China and abroad have proposed a lot of practicaland effective topology control algorithms, but all of them have a few disadvantages. Thispaper makes a brief introduction of WSN at first, summarizes the present developingsituations, characteristics and prospects of application of WSN，describes the presentresearching situations, designing ideas, performance evaluations and problems which needstudying of topology control algorithms from the angle of energy conservation. In view of theadvantages and disadvantages of current topology algorithms, the improved LEACH of theenergy efficiency and sector distribution called MHS-LEACH and a proactive maintainingalgorithm for dynamic topology control called PMD in WSN are both proposed in this paper.The classical clustering algorithm LEACH and its improved algorithm ID-LEACH inWSN are introduced in detail at first, and then the problem that LEACH selects cluster headswithout considering the residual energy and the problem of the large energy consumptionduring the direct communication between cluster heads and the sink node are both analyzed.The definition ‘balance factor’ is introduced in MHS-LEACH, cluster heads can be adjustedaccording to the nodes’ residual energy, and the consideration of the residual energy in thestage of selecting cluster heads can balance the network energy consumption. At the sametime, MHS-LEACH achieves the goal of energy efficiency by dividing sensing area intovirtual sectors. Distributing cluster head IDs according to virtual sectors makes cluster headssearch their father nodes within the same sector and tree links realize the multi-hopcommunication between cluster heads and the sink node.The simulation experiment and data analysis are made for MHS-LEACH in the networklifecycle, residual energy and nodes’ energy consumption. The experimental results indicatethat, compared with LEACH and ID-LEACH, MHS-LEACH not only chooses nodes with abig proportion of residual energy as cluster heads, makes nodes avoid dying quickly after being chosen as a cluster head in a short time, but also distributes IDs for cluster headsdepending on virtual sectors, builds the effective multi-hop tree links among cluster heads,prolongs the life time of WSN efficiently and balances the energy consumption of the wholenetwork.The classical topology control algorithm XTC, its improved algorithm PLBD and Poly inWSN are also introduced in detail, the problem of selecting the link quality metrics and theproblem that the incomplete topology maintenance mechanism leads to the topologydestroying by invalid nodes and the network partitions are both analyzed. PMD marks thevisited nodes and builds a set called ‘FOUND’ for them to improve BFS (Breadth-FirstSearch) based on the original one, and then adds the operation of controlling its startingmoment by comparing the number of elements in ‘FOUND’ and the total number of nodes inWSN, achieves to recognize the addition of invalid nodes and monitor the network structuredynamically. Only after network partitioning happens does PMD start the link rebuildingmechanism to maintain the topology and reorganize the partitions. The definition,‘Communication Quality’, is proposed to measure the quality of communications link as thelink quality metric. The Minimum Spanning Tree(MST) in Kruskal algorithm is used toreconstruct the parted network, guaranteeing the network connectivity, restraining the isolatednodes’ generation and making the energy be used efficiently.The simulation experiment and data analysis are made for PMD in the number ofisolated nodes and effective nodes. The experimental results indicate that, compared withXTC, PLBD and Poly, PMD not only identifies the moment of the network partitioning by theimproved BFS, monitors the network connectivity in time, but also reconstructs the partednetwork proactively by the Minimum Spanning Tree (MST) to maintain the topology,improves the energy efficiency and availability of WSN, balances the energy consumption ofthe whole network and achieves a topology with better connectivity and robustness.