Research On Node Scheduling Schemes In Wireless Sensor Networks

Wireless sensor network is a multi-hop ad hoc network consisting of a large number of sensors deployed in the monitoring region. Sensor network has promising prospects in many areas such as military monitoring, environment surveillance and telemedicine, since it is easy to deploy and operates with low cost and low power. Due to the severe energy constraint of the sensor nodes, wireless sensor network can hardly satisfy the long-term operation demand. How to use the resource limited sensor nodes to achieve the desired network lifetime is a fundamental problem of wireless sensor network. Node scheduling scheme is the most frequently used approach in literature; by putting redundant nodes into sleep mode and keeping only a subset of sensors active, node scheduling scheme can reduce the energy consumption and prolong the network lifetime effectively.Based on IEEE 802.11 MAC protocol, this thesis focuses on extending network lifetime while satisfying application demand. Specifically, the following problems are studied in this paper.An energy efficient coverage based node scheduling algorithm Energy aware Coverage based Node Scheduling scheme (ECNS) is proposed to prolong network lifetime while maintaining network coverage, network connectivity and sensor self-protection. ECNS enables each node to decide whether it is eligible to turn off to conserve energy through local information exchange with its neighbors. ECNS is characteristic of its fully distributed manner, low overhead and load balance. The cluster-based routing algorithm, LEACH, is implemented to evaluate the performance of ECNS; simulation results show that ECNS can improve the network performance with respect to energy conservation, load balance and network lifetime.Considering the lack of node scheduling algorithm based on continuous monitoring of isolated targets, a novel distributed node scheduling algorithm, Continuous Target Monitoring based Node Scheduling scheme (CTMNS) is put forward in this thesis. To improve the energy efficiency and extend the network lifetime for isolated targets monitoring applications, CTMNS activates only a subset of sensors in the network to provide desired coverage level for multiple isolated targets. In CTMNS, each sensor is associated with a location-and-energy dependent weight, which evaluates the sensor's significance in terms of target monitoring. Each sensor calculates its associated weight individually and determines its redundancy eligibility through local communication with its neighbors based on the Redundancy Eligibility Rule. By turning off redundant nodes, CTMNS prolongs network lifetime while providing differentiated coverage for multiple targets. Simulation results show that CTMNS prolongs the network lifetime to 2.7 times that of non-scheduled target monitoring scheme.