Wake-up Scheduling for Event Monitoring in Wireless Sensor Networks

Abstract

The attention is on critical event monitoring in wireless sensor networks (WSNs), where only a small
number of packets need to be transmitted most of the time. When a critical event occurs, an alarm message should be
broadcast to the entire network as soon as possible. To prolong the network lifetime, some Wakeup scheduling methods
are always employed in WSNs, resulting in significant broadcasting delay, especially in large scale WSNs. A novel
Wakeup scheduling method is proposed to reduce the delay of alarm broadcasting from any sensor node in WSNs.
Specifically, two determined traffic paths are designed for the transmission of alarm message, and level-by-level offset
based wake-up pattern according to the paths, respectively. When a critical event occurs, an alarm is quickly transmitted
along one of the traffic paths to a center node, and then it is immediately broadcast by the center node along another
path without collision. Therefore, two of the big contributions are that the broadcasting delay is independent of the
density of nodes and its energy consumption is ultra low. Exactly, the upper bound of the broadcasting delay is only 3D
+ 2L, where D is the maximum hop of nodes to the center node, L is the length of Wakeup duty cycle, and the unit is the
size of time slot