A study of long-term WSN deployment for environmental monitoring

In this paper, the ASWP testbed, a long-term wireless sensor network (WSN) deployment for environmental monitoring, is presented. This testbed implements a periodic sampling application for external sensors exposed to a forested outdoor environment in western Pennsylvania, USA. It has been running for the past two years using TinyOS-based WSN platforms and the commercially available routing software XMesh. ASWP´s performance is analyzed in detail for the period of August 2011 to August 2012, focusing on packet duplication, packet loss, and network maintenance. The results indicate that the critical impact due to the outdoor environment and node physical failures significantly reduced the network yield when long-term periods were considered. In particular, it is found that an over-used routing path across the network was responsible for most of the packet retransmissions and drops in ASWP. This work intends to provide a reference point for WSN research and development targeted towards outdoor WSNs for long-term deployments.