Research On Delay Optimization Scheme For Duty-cycled Wireless Sensor Networks

Wireless sensor network is a self-organized multi hop network that consists of a large number of cheap micro sensor nodes.These sensor nodes carry limited resources,which severely restricts the network lifetime.Wireless sensor network usually uses wake-up/sleep alternate duty-cycling mode to save energy.At the same time,it is also accompanied by the serious delay problem,which is fatal to some delay sensitive wireless sensor network applications.Therefore,how to quickly and efficiently transmit data to sink while ensuring the network lifetime has always been the focus and difficulty of research.In this thesis,we research the above problem and research the following issues:(1)Aiming at the poor optimization effect of the existing schemes on end-to-end delay,we propose a duty cycle and transmission power control scheme for delay minimization to realize the comprehensive optimization of energy and delay.The scheme introduces the concept of residual energy coefficient and divides the residual energy of node into two parts.One part is used to increase the duty cycle and the other part is used to increase the transmission power,which can reduce the network delay.It is proved theoretically that in a bounded planar wireless sensor network,there must be an optimal residual energy coefficient for any node in the network,so that the end-to-end delay of the node is optimal.Based on this,the scheme designs an approximate optimization algorithm to find the best residual energy coefficient,thus achieving the goal of minimizing end-to-end delay.Theoretical analysis and simulation experiments show that under the same network lifetime,compared with the traditional scheme,the scheme can reduce the network delay by 60.1%-78.4% and improve the energy utilization by 11.6%-17.2%.Compared with dynamic duty cycle scheme,the scheme can reduce network delay by 24.3%-39.7%.(2)Considering that different network applications have different requirements for end-to-end delay,we propose an end-to-end delay optimization scheme based on fast forwarding node,which meets the endto-end delay requirements of applications by selecting a certain proportion of fast forwarding nodes in the network.The fast forwarding node can keep working all the time.Once it is selected as the relay node,there will be no sleep delay in data transmission,so as to reduce the network delay.The scheme rotates the fast forwarding nodes periodically according to the residual energy to ensure the network lifetime and make the network energy consumption more balanced.Theoretical analysis and simulation experiments show that the scheme can not only meet the given end-to-end delay requirements,but also ensure that the network lifetime is not lower than previous scheme.