Self-Adjustable Active Sequence to Reduce Latency in Duty Cycle WSNs

The wireless sensor networks (WSNs) have a great application prospect, which is composed of much simple hardware and small-size sensor nodes to realize the perception of the surrounding environment. It is often widely used that nodes work in a duty cycle mechanism of periodic sleep and awakening in WSNs. However, this mechanism also increases latency and the routing table length whereas saving energy. In this paper, the Self-adjustable Active Sequence (SAC) scheme is proposed to solve the above problems. It enables optimization of energy, latency and routing tables. The main innovations are as follows. Firstly, the SAC scheme divides the continuous active slots into multiple shorter slots to reduce the latency. Second, SAC scheme adds more active slots by using the remaining energy. Third, decreasing the number of the forwarding nodes to reduce the routing table length. In this case, the optimization of delay only brings small gains, so we should focus on the improvement of routing. It has a better performance in reducing the delay and reducing the length of the routing table through both theoretical analysis and experimental results. If and only if the continuous active slots are divided into several segments, the delay is reduced by 33%. And the number of active slots by using the far sink region energy further reduce the delay by 29% in general. What's more, when reducing the size of the forwarding nodes set, the routing table length is further reduced by 29%.