Research And Design Of Reprogramming On WSN Nodes

A Wireless Sensor Network (WSN) is a network consisting of spatially distributed autonomous devices. These devices use their sensors to monitor environmental conditions, such as temperature, sound, pressure, vibration, and so on. Decision is made after data acquisition and information processing. WSNs were originally motivated by military applications, such as battlefield surveillance. In addition, WSNs are broadly used in many civilian application areas, including environment monitoring, home automation, and traffic control. WSNs become one of the hottest research directions of computer science nowadays.WSNs consist of a large number of sensor nodes which have the capability of computing, sensing and communicating. Most sensor nodes are low-cost and resources-constrained compared to other embedded systems, so it can be deployed in a large scale. Energy efficiency is one of the most challenging issues since most of the sensor nodes are battery powered. The software in a deployed WSN often needs to be changed, e.g., updating the system with new functionality, or fixing software bugs. Hence, reprogramming of WSNs is an desired feature. Usually a large number of sensor nodes are spread over a large field which is usually unreachable. Updating software manually is impossible. So network managers need remote reprogramming ability in order to add new functionality or fix software bugs.In this thesis, we propose a reprogramming technique for sensornet operating systems. First, we analyze and summarize existing solutions on sensornet OSes. Then we propose our solution based on the design of loadable modules. We use Executable and Linkable Format (ELF) for the loadable modules. As all ELF data structures were originally designed for 32-bit platforms, it is costly for 8-bit or 16-bit platforms such as the sensor node hardware. What is more, there are others extra overheads in the ELF file. So we have designed a new file format that is more compact than the standard ELF. In order to speedup the load-time, we propose the pre-linking technique. The benefit of pre-linking is that the process of loading the modules on nodes is less complex, as the linking process is done at base station. Finally, experiments have been carried out to demonstrate the efficiency the proposed solution.