Details of Research Outputs

Fast and energy efficient transmission is an important and challenging issue for wireless sensor networks (WSNs). Energy efficiency is also an important concern of green communication in WSNs. Optimizing the duty cycle (DC) of nodes and the size of forwarding node-set (SFNS) can effectively reduce the delay and improve energy efficiency. In this paper, we conclude that an optimal DC value can minimize the delay when the number of SFNS is constant. The reason why the delay is larger when the DC is smaller than the optimal value is that when the sender sends data, it needs to wait for the forwarding node to wake up which causes a large delay. When DC is larger than the optimal value, the delay is also larger because SFNS has more than one node in the awake state, which causes conflicts and increases the delay. For energy consumption, the sender with smaller DC has fewer collisions, so the energy consumption is less. Similarly, when DC is constant, SFNS also has an optimal value, which minimizes the delay. Based on the theoretical analysis, an Optimization Duty-Cycle and Size of Forwarding Node Set (ODC-SFNS) scheme is proposed to reduce delay and improve energy efficiency. The main optimization methods adopted are as follows: (a) For dense and high-DC networks, one hop delay and the number of hops needed for the packet to reach sink can be reduced by appropriately limiting the SFNS, thus the end-To-end delay can be effectively reduced. (b) For sparse and low-DC networks, increasing the DC in the far sink region can reduce delay while not reducing the network life, and improve energy efficiency. Compared with the traditional scheme, the ODC-SFNS scheme can reduce the end-To-end delay by 20.52%-79.96%, and it has dramatically increased energy efficiency. Moreover, its scope of application is broader than previous strategies.