A link quality estimation model for energy-efficient wireless sensor networks

Understanding fluctuations of link quality in a wireless sensor network is useful for different reasons. For example, nodes can determine when and for how long they should transmit packets, so that they can reduce packet loss rate and the cost of retransmission (delay as well as power consumption). However, because the quality of a link depends on many factors, it cannot be known except in a probabilistic sense. In this paper we estimate the expected duration in which the quality of a specific link remains stable using the conditional distribution function of the signal-to-noise ratio (SNR) of received acknowledgment packets. We employ the expected duration to determine how long nodes should transmit packet in burst and how long they should refrain from contention. To develop our model, we deployed Imote2 sensor platforms in indoor and outdoor places and transmitted more than 70, 000 packets. We transmitted additional 16,900 packets to test our model. 90% of the time, our approach resulted in high packet delivery compared with the case in which packets were transmitted without knowledge of link quality fluctuations.