Research On Algorithms For Topology Control In Wireless Sensor Networks

In recent years,wireless sensor network has become a popular and important technique of information acquisition,which enables people to collect various reliable, real-time data anywhere,any time,under any circumstances.Hence,it has lots of potential applications in various fields,and thus has become an academic hot spot.Topology control is one of the key fundamental techniques in the design of wireless sensor networks,which,under the condition of preserving required degree of coverage and connectivity,helps sensor nodes to form an optimized network topology through sleep scheduling,power control and neighbor selection.After topology control is applied, the network lifetime is prolonged,interference reduced,and throughput increased.At the same time,topology control can provide the network infrastructure required by other functional module.Focusing on two problems,we study on the topology control in wireless sensor networks in this thesis.Many energy-efficient routing protocols depend on the planarity of the network topology,however,previous planar topologies were constructed stationarily in a fixed manner on a network-wise basis,which not only neglects the influences of the traffic and channel status varying according to time and space,but also that of the residual energy of sensor nodes.To address this problem,we propose a t-adjustable planar structure, denoted by TAP,and its construction algorithm in this thesis.This structure is based on the proximity of neighboring nodes and removes links according to specific rules.Sensor nodes running the construction algorithm can adjust the topology by parameter t according to local network dynamics.We prove by analysis and simulation some important properties of TAP.TAP is planar,connected,symmetric and sparse;TAP is guaranteed to contain the minimum energy consumption path between any pair of nodes when all nodes have t=1;the transmission power,interference and node degree decrease as t increases;in addition,maximum node degree in TAP is bounded by 6 when all nodes have t=3.Existing approaches to maintain network coverage and connectivity in three-dimensional sensor networks are based on the assumption of homogeneous sensor nodes and only guarantee 1-connectivity.To resolve this problem,we theoretically analyze the sufficient conditions to maintain m-coverage,k-connectivity,and reduce transmission power in three-dimensional heterogeneous sensor networks,deriving some design rules.Based on these rules,we then designed an integrated topology control algorithm to maintain k-connectivity and m-coverage which takes into account both sleep scheduling and power control.The simulation results show that the proposed algorithm efficiently prolongs network lifetime while preserving required network connectivity and coverage.