On the Need for Passive Monitoring in Sensor Networks

Debugging and analyzing wireless sensor networks (WSNs) are important tasks for improving the quality and performance of the network. In this paper, Pimoto is to be presented, which is a distributed passive monitoring system implemented for debugging and analyzing WSNs. It is based on a hierarchical structure allowing to monitor different networks simultaneously and to analyze the obtained information at a dedicated PC. The system relies on three components. The first element is the monitoring node. It intercepts the radio packets in the vicinity and sends received packet information to a gateway using a second radio interface in order to prevent intrinsic interactions with the sensor network operation. The gateway has the ability to communicate directly with the monitoring node and to transfer all the collected monitoring data to the third component, a dedicated PC (server), in the hierarchy using standard TCP/IP communication. The packets are analyzed and visualized on the server using the standard network monitoring and analyzing tool Wireshark. The most important characteristic of this monitoring concept is the passive operation, i.e. the normal operation in the WSN is not influenced by the analyzer.