This paper presents DISSense, an adaptive, ultralow-power communication 
protocol for wireless sensor networks. DISSense is specifically designed for 
long-term environmental monitoring applications and it provides for both data 
collection and data dissemination services. By automatically adapting the 
length of its active phases, DISSense can guarantee for both a very low duty 
cycle and reliable data delivery. We tested the performance of DISSense on 
both a testbed and on the TOSSIM simulation environment. Our experimental 
results show that a sensor network running DISSense can provide for average 
data delivery ratios above 98% and at the same time achieve a lifetime of 
several years. Our TinyOS 2.1 implementation of DISSense is publicly available.