Efficient and portable reprogramming method for high resource-constraint wireless sensor nodes

Wireless sensor networks (WSNs) will play a significant role in precision agriculture to support sustainable development. Since it´s a more economic and practical solution to deploy reprogrammable sensor nodes than non-reprogrammable ones, sensor node reprogramming technique becomes a key issue. Currently, the challenge of sensor node reprogramming mainly results from the resource constraint and diverse platforms in WSNs. In our work, we firstly ported a small footprint Java Virtual Machine simpleRTJ to wireless sensor nodes based on AT91SAM7S256 microcontroller for a reprogramming task. This method not only facilitates the application development but also shows its advantage in heterogeneous environments. However, the high memory resource requirement of simpleRTJ makes it inappropriate for some ultra low power 8-bit microcontrollers, such as ATMEGA1281, which has particularly constrained resource. Thus we propose a new efficient and portable reprogramming method (EPRM) by using pre-linked native code to reduce memory footprint and by the way to reduce energy consumption. To validate this new approach, EPRM is implemented on two platforms (32-bit and 8-bit cores) and its efficiency in terms of resource consumption (memory and energy) is evaluated by comparing with simpleRTJ ones. The obtained results show that EPRM is well adapted to high resource-constraint wireless sensor nodes.