End-to-End Acknowledgement for Data Collection in Wireless Sensor Networks

A novel method to improve the reliability of data collection in wireless sensor networks is presented. The Disseminated ACKnowledgment protocol (DACK) builds on collection and dissemination protocols to provide end-to-end acknowledgement of data samples. A DACK protocol implementation was tested using simulations and experiments on TelosB motes running TinyOS 2.1. Experiments were carried out on three floors of a building, with 14 motes transmitting data samples continuously until battery exhaustion. Results show that the DACK protocol recovers all data samples that would have been lost using a collection protocol only. The benefit of increased data collection reliability comes at the cost of increased communication. In one experiment with 14 motes, 719 data samples were dropped from a total of 749,904 data samples sent over six days; all these dropped samples were recovered using the DACK protocol. This experiment required an additional 720 collection packets to resend the dropped samples (in addition to the original 467,778 collection packets) plus 18,733 DACK packets. The extra energy required to send these DACK packets was determined experimentally to be negligible. The DACK packet to original collection packet ratio of 0.04 in the experiment was observed to increase to 0.078 in a simulation of 16 motes in a much noisier 4 by 4 grid network.