PMC: An Energy Efficient Event Transport Service For Wireless Sensor Network

A wireless sensor network is normally a multi-hop wireless ad hoc network whose purpose is to transmit events sensed by sensors to the sink. Since sensor nodes are normally powered by non-rechargeable and non-replaceable battery, an energy efficient event transport service is crucial for extending the life time of a wireless sensor network. Due to the possibility of crossing multiple lossy links between the source and the sink, many events may be lost before they arrive at the sink. In addition, the overhead of low layer protocols is very large due to the short event data. These two factors can result in significant event loss and waste of energy. Many mechanisms have been proposed on other networks to improve reliability and reduce overhead. Due to scarce memory and poor computing ability of sensor nodes in a sensor network, these mechanisms may not be feasible to implement and they may not work efficiently with respect to energy. In this paper, PMC (Pipelined Multiple Copies) is proposed for transmitting events in a wireless sensor network, with the goals of achieving low event loss rate and high energy efficiency. In PMC, multiple copies of an event are pipelined and transmitted in several consecutive frames according to Silent CSMA, a variant of CSMA/CA. Multiple copies of an event reduce end-to-end event loss rate and Silent CSMA reduces packet energy consumption significantly.